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immunology

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A

active immunity

immunity acquired through exposure to antigen and response of one's own immune system.

acute phase protein

protein produced in response to infection, usually within a few hours to a few days. Acute phase proteins signal an activation of the innate immune system and are not antigen-specific.

adaptive immunity

immunity acquired through responses of antigen-specific lymphocytes, resulting in immune memory.

ADCC

Antibody-Dependent Cell-mediated Cytotoxicity, killing of target cells by K cells with specific antibody bound to their Fc receptors.

adhesion molecule

cell surface molecule that allows cells to adhere to other cells.

adjuvant

molecule that increases the immune response to an antigen. Adjuvants are often given with vaccines.

adoptive transfer
creation of experimental immune system by destroying the host's immune system with irradiation and replacing it with lymphoid cells from another animal or person. Used to study function of certain populations of cells and lymphoid development.
affinity

attraction between two molecules; the higher the affinity, the higher the probability they will bind and stay bound to one another.

affinity chromatography

separation of molecules based on their affinity for immobilized ligand.

affinity maturation

increase in antibody affinity observed as an immune response progresses.

agglutination

clumping of cells, often induced by antibodies.

AIDS

Acquired Immune Deficiency Syndrome, the disease caused by HIV.

alkylosing spondylitis

autoimmune disease resulting in inflammation in the spinal column.

alleles

copies of the same gene on two different chromosomes. Alleles may be identical (homozygous) or non-identical (heterozygous).

allergen

antigen that induces an allergic response.

allergy

immune response to (usually) noninfectious agent; Type I hypersensitivity.

allogeneic

differing between members of the same species.

allograft

graft from another member of the same species.

alloreactive T cells

T cells that make an immune response to cells from another individual; T cells responsible for graft rejection.

allotype

antigenic epitope differentiating antibody (or other) molecules from different individuals.

alternative complement pathway

complement pathway initiated by contact with bacterial antigens.

anamnestic response

also called memory response; heightened response to repeat antigen exposure.

anaphylatoxin

substance that induces inflammation, released in response to complement activation.

anergy

lack of immune response.

angioneurotic edema

tissue swelling (edema) resulting from complement activation due to a deficiency of the complement regulatory protein C1 inhibitor.

antibody

serum protein made in response to antigen; also called immunoglobulin (Ig).

antigen

molecule that induces antibody production; also, molecule specifically bound by antibody or TCR.

antigen binding

physical association of antigen with antibody, TCR, or MHC.

antigen processing

enzymatic digestion of antigen and association with MHC for presentation to T cells.

antigenic drift

mutation resulting in small change in antigen structure.

antigenic shift

mutation resulting in large change in antigen structure.

antigenic variation

selection for infectious agents that have mutated antigens which are different from those originally recognized by the immune system.

APC

Antigen-Presenting Cell: B cell, dendritic cell, or macrophage that displays antigen on MHC for T cell activation.

apoptosis

programmed cell death.

appendix

collection of immune system tissue near the junction of the small and large intestines; part of the MALT.

Arthus reaction

localized inflammatory reaction, usually observed in the skin.

ascites tumor

tumor growing in the peritoneal cavity.

atopy

predisposition to becoming allergic.

attenuated vaccine

vaccine which uses live but weakened organism to induce immunity.

autograft

graft of tissue from one part of the body to another.

autoimmunity

immune response made against self antigens.

autoradiography

detection of molecules by detecting radioactive tags attached to them.

avidity

combined affinities in multivalent binding.

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B

B cell

lymphocyte which develops in the bone marrow and binds antigen with membrane antibody (immunoglobulin).

b2 microglobulin

part of the Class I major histocompatibility molecule (MHC)

B7

membrane co-stimulatory molecule, participates in activation of B cells and macrophages.

bare lymphocyte syndrome

immune deficiency resulting from a deficiency of some or all MHC molecules.

basophil

granulocytic white blood cell with cytosolic granules that stain with basic dyes.

BCR

B Cell (antigen) Receptor, also called membrane immunoglobulin (mIg).

Bence Jones protein

free antibody light chains excreted in the urine of individuals with plasma cell tumors (multiple myelomas).

blot

transfer of protein or nucleic acid fragments from electrophoresis gel to nitrocellulose paper, to which they bind tightly, for antibody binding or nucleic acid hybridization analysis.

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C

 
C1 INH

C1 inhibitor, a regulatory molecule that inhibits complement C1 activity.

C3 convertase

complement molecules that activate complement C3.

C5 convertase

complement molecules that activate complement C5.

calnexin

chaperone that promotes the successful binding of processed antigen and MHC.

calreticulin

chaperone that promotes the successful binding of processed antigen and MHC.

CAM

Cell Adhesion Molecule; membrane molecule that allows cells to adhere.

carrier protein

protein covalently linked with a small molecule (hapten) to increase the hapten's ability to induce immunity.

CD antigen

Cluster of Differentiation; membrane proteins on immune system cells that allow for their identification and isolation.

CD3

part of the T cell (antigen) receptor complex. CD3 transduces the antigen binding signal outside the plasma membrane into chemical signals (phosphorylation) in the cytoplasm.

CD4

co-receptor on helper T cells that binds Class II MHC and participates in T cell activation by antigen.

CD8

co-receptor on cytotoxic T cells that binds Class I MHC and participates in T cell activation by antigen.

cDNA library

collection of cDNA (complementary DNA) sequences from the mRNA of an organism in vectors; includes only exon DNA sequences from expressed genes.

cell adhesion molecule

membrane molecule that allows cells to adhere (CAM).

cell line

cells which can be cloned and propagated indefinitely in tissue culture.

cellular immunity

immunity which can be transferred between individuals with the transfer of T cells.

central lymphoid organ

bone marrow or thymus; lymphoid organ where lymphocytes develop.

chaperone

molecule that promotes the folding or prevents denaturation of another protein; see calnexin and calreticulin.

chemokine

small molecule secreted by white blood cells that attracts leukocytes.

chemotaxis

movement of a cell in a chemical gradient, promoted by chemokines and anaphylatoxins.

chimera
an individual with part or all of their immune system from another individual. The name comes from the mythological beast which is part lion, part goat, and part snake.

model of a chimera

chimeric antibody

antibody encoded by genes from more than one species, usually with antigen-binding regions from mouse genes and constant regions from human genes.

51Cr release

method for detecting cell-mediated cytotoxicity by allowing cells that will be lysed to take up a radioactive isotope of chromium into their cytosol; death results in the release of the chromium into the culture fluid.

chronic desensitization

exposure to very low doses of allergen over time to decrease allergic reactions to that allergen.

chronic granulomatous disease

disease characterized by the presence of many granulomas, small nodules of inflammatory cells, usually associated with persistent infections or autoimmune inflammation.

Class I MHC

MHC proteins that present antigen synthesized in an infected cell's cytosol to cytotoxic T cells.

Class II MHC

MHC proteins that present antigen taken up in phagocytic or endocytic vesicles to helper T cells.

classical complement pathway

activation of complement by binding to antigen-antibody complexes.

CLIP

the part of the chaperone invariant chain (Ii) which occupies the peptide-binding site of class II MHC during folding in the endoplasmic reticulum and prevents binding of endogenous peptides. CLIP is removed in the MIIC vesicle by DM so that exogenous peptide can bind.

clonal deletion

elimination of all lymphocytes that bind a particular antigen; mechanism that normally prevents autoimmune reactions.

clonal selection

stimulation of antigen-specific lymphocytes to proliferate and become active effector cells that eliminate that antigen.

clone

many identical copies of a gene or a cell, produced from a single precursor.

co-stimulation

signal(s) that must accompany antigen stimulation of effectively activate lymphocytes.

complement

collection of plasma proteins that can be activated to promote inflammation and antigen elimination. They complement (work with) antibody (note absence of "i" in this complement).

complementary DNA (cDNA)

DNA that has been copied from an mRNA template and is complementary in base sequence to that RNA; it should be identical in base sequence to the DNA from which the mRNA was transcribed (minus any introns and regulatory regions).

congenic mice

mice that have been bred to differ at only one MHC gene

cosmid vector

plasmid vector which contains the cos site of lambda phage DNA for insertion of a gene, a replication origin so the vector will replicate, and a drug-resistance gene so cells into which the vector has been inserted can be selected.

cross-reactivity

the binding of a ligand similar to but not identical with the specific ligand. For example, an antibody to antigen A may cross-react (bind to) antigen A'. Some antibodies to Streptococcus pyogenes bind to human heart tissue, resulting in rheumatic heart disease.

cyclosporin A

drug that suppresses the immune system, specifically T cell activation.

cytokine

small molecule secreted from one cell that signals another cell by binding to its specific receptor.

cytokine antagonist

molecule that interferes with cytokine function.

cytokine pleiotropism

a cytokine has more than one function.

cytokine receptor

membrane molecule that specifically binds cytokine.

cytokine redundancy

more than one cytokine has the same function.

cytokine synergism

ability of cytokines to act together to promote more activity than either can generate alone.

cytosolic processing pathway

pathway for processing cytosolic (endogenous) antigen for presentation on class I MHC.

cytotoxic T cell

T cell which kills virus-infected cells and tumor cells.

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D

DAG

diacylglycerol, a cytoplasmic second messenger in lymphocyte activation; activates protein kinase C.

dendritic cell

cell with long processes (dendrites) that presents antigen.

DM

class I MHC molecule which facilitates the removal of CLIP and the binding of exogenous peptide to class II MHC molecules in the MIIC vesicle.

DNA footprinting

technique for identification of a regulatory sequence in DNA; binding of a regulatory protein protects the DNA from restriction endonuclease cleavage.

DNA vaccine

vaccine in which antigen DNA is injected and expressed in host cells; the expressed antigen stimulates an immune response.

double negative T cell

immature T cell which expresses neither CD4 nor CD8 on its membrane.

double positive T cell

immature T cell which empresses both CD4 and CD8 on its membrane.

DTH

Delayed Type (Type IV) Hypersensitivity. Th1 cells activate macrophages to eliminate antigen.

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E

 
early induced response

innate response to antigen which requires protein synthesis and involves inflammation but is not antigen specific.

EBV

Epstein Barr Virus; infects B cells.

eczema

skin rash, often occurs in response to antigen.

effector cell

activated cell which participates in antigen elimination.

electroporation

technique used to get cloned DNA into a cell; an electric current causes pores to form in the cell's membrane through which DNA enters.

ELISA

Enzyme-Linked ImmunoSorbent Assay, which detects antigen-antibody binding using antibody complexed with an enzyme that forms a colored product from a colorless substrate.

endogenous antigen

antigen synthesized in the cell cytoplasm, presented on class I MHC.

endoplasmic reticulum (ER)

membrane-bound cell compartment where proteins destined for the plasma membrane or for secretion are transported after synthesis, and where endogenous peptides are transported for binding to class I MHC.

endosomal processing pathway

pathway for processing phagocytosed or endocytosed (exogenous) antigens for presentation on class II MHC.

endotoxin

toxin which is part of the bacterial structure. Usually refers to lipopolysaccharide (LPS) in the Gram negative outer membrane.

enhancer

regulatory region of DNA which increases gene transcription.

env

protein antigen(s) in the viral envelope. env, the gene for the envelope protein(s).

enzyme

organic reaction catalyst, which facilitates a chemical reaction without being used up. Most enzymes are proteins, but some RNA has catalytic activity for processing mRNA.

eosinophil

granulocytic white blood cell with cytosolic granules that stain with acidic dyes (eosin). Eosinophils have Fc receptors for IgE and are efficient at killing worm parasites.

epidemiology

study of disease transmission.

epitope

part of antigen bound by antibody or TCR.

equilibrium dialysis

technique used to measure antibody affinity.

erythroblastosis fetalis

hemolytic disease of the newborn. Rh negative mother makes anti-Rh antibody which can cross the placenta and lyse the erythrocytes of the Rh positive fetus.

erythrocyte

red blood cell (RBC); carries oxygen to the tissues and carbon dioxide to the lungs.

exogenous antigen

antigen synthesized outside the APC, phagocytosed or endocytosed into vesicles, and processed for presentation on class II MHC.

exon

coding region of a gene; base sequence that is expressed in the protein sequence.

experimental autoimmune encephalitis

laboratory model for multiple sclerosis, induced by injecting myelin basic protein.

extravasation

process by which leukocytes move from the circulation into the tissues.

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F

Fab

antigen-binding region of antibody molecule; named for the antigen-binding fragment of enzymatically digested antibody.

FACS

Fluorescence-Activated Cell Sorter; equipment used to count and separate leukocytes labeled with fluorescent-tagged antibodies to cell surface molecules.

Fas

membrane molecule which, when bound by FasL, initiates apoptosis.

FasL

ligand for Fas

Fc

constant region of antibody heavy chain; named because it was in the crystalizable fragment of enzymatically digested antibody.

FcR

receptor for antibody Fc.

FDC

Follicular Dendritic Cell. Found in the B cell areas of secondary lymphoid organs and participates in B cell activation.

fever

increase in body temperature over the normal 98.6F (37C).

Ficoll Hypaque

material used to separate leukocytes by their density, especially lymphocytes from other white blood cells and erythrocytes.

FK506

immunosuppressant drug.

flow cytometry

process used to detect and quantify fluorescent antibody bound to leukocytes.

fluorochrome

small fluorescent tag which allows for detection of antibodies.

follicle

in immunology, an area of the spleen or lymph node occupied by B cells and FDC.

fragmentins

enzyme present in the granules of cytotoxic T cells and NK cells which induce apoptosis in the target cells. Also called granzymes.

framework region

regions of the antibody molecule which do not bind antigen but whose structure allows for folding of the antibody so all the contact regions bind antigen.

Fv antibody

manufactured antibody molecule composed of one or more variable regions with no Fc.

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G

gag

protein antigen(s) in the virus capsid. gag, gene for viral capsid protein(s).

gamma delta T cells

T cells with TCR composed of gamma and delta chains instead of the more usual alpha and beta chains.

gamma globulin

fraction of serum which contains most antibody molecules.

GALT

gut-associated lymphoid tissues

germinal center

concentration of rapidly dividing B cells in the spleen and lymph nodes.

gel electrophoresis

technique used to separate proteins and fragments of DNA or RNA. Molecules move through a polyacrylamide or agarose gel in response to an electric current. In the most common technique, smaller molecules move faster and travel farther than larger molecules.

gel-shift analysis

technique for identifying regulatory regions of DNA by their altered electrophoretic mobility in the presence of protein regulators.

gene expression

production of mRNA and synthesis of a functional protein

genome

nucleic acids representing entire genetic information of an organism; in humans, all 46 chromosomes.

genomic DNA library

collection of DNA sequences from an organism, including introns and regulatory regions, in lambda phage DNA vectors.

genotype

genetic characteristics encoded in the DNA of a cell or organism.

GlyCAM

cell adhesion molecule used by lymphocytes to enter the lymphoid tissues.

GM-CSF

growth factor for granulocytes and monocytes.

Goodpasture's syndrome

autoimmune disease in which vascular disease is caused by autoantibodies to Type IV collagen or basement membrane.

graft rejection

immune process that kills transplanted non-self tissue.

granulocyte

leukocyte with a lobed nucleus and prominent cytoplasmic granules. Basophils, eosinophils, and neutrophils are granulocytes. Also called polymorphonuclear leukocytes (PMNs).

granzyme

enzymes present in the granules of cytotoxic T cells and NK cells which induce apoptosis in the target cells. Now called fragmentins.

Greek letters used in immunology (how to keyboard).
If you don't have the proper symbols, spell out the name of the letter (a or alpha, not a).

a alpha (symbol a)
b beta (symbol b)
g gamma (symbol g)
d delta (symbol d)
e epsilon (symbol e)
z zeta (symbol z)
h eta (symbol h)
q theta (symbol q)
k kappa (symbol k)
l lambda (symbol l)
m mu (symbol m)
f phi (symbol f)

GVHD

Graft Versus Host Disease. The rejection process when transplanted allogeneic bone marrow recognizes host MHC as foreign.

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H

H-2

mouse major histocompatibility locus and antigens.

HAMA response

Human Anti-Mouse Antibody. Antibody made by humans against mouse monoclonal antibodies used to treat cancer or autoimmunity.

haplotype

all genes inherited from one parent; half of one's genome.

hapten

small molecule which is immunogenic only when covalently linked to a carrier molecule. In effect, one antigen epitope.

helper T cell

regulatory T cell which used cytokines to stimulate B cells to produce antibodies, macrophages to become activated, or cytotoxic T cells to become effector CTL.

hematopoiesis

the process of blood cell formation. Hematopoiesis occurs in the yolk sac and the liver during early fetal development and in the bone marrow thereafter.

hemolysis

lysis of erythrocytes.

heterozygous

having non-identical copies (alleles) of a gene from each parent.

HEV

High Endothelial Venules. Specialized cells lining the capillaries in the lymphoid organs where leukocytes enter from the circulation.

hinge region

flexible region of IgG and IgA antibody molecules. The hinge region connects the Fc and Fab regions and facilitates binding of both Fab regions to nearby antigen epitopes.

histamine

molecules in the granules of mast cells which, when released, dilate blood vessels and cause smooth muscle contraction.

HIV

Human Immunodeficiency Virus, the virus that causes AIDS.

HLA

Human Leukocyte Antigen, human MHC.

HLA-DM

Class I MHC molecule which facilitates the removal of CLIP and the binding of exogenous peptide to Class II MHC molecules in the MIIC vesicle.

homozygous

having identical copies (alleles) of a gene from both parents.

humanized antibody

genetically engineered mouse antibody in which the Fc (and sometimes the framework) regions have been replaced with human sequences to prevent a HAMA response.

humoral immunity

immunity that can be transferred from one individual to another with serum; i.e., antibody formation.

hybridization

specific binding of two complementary strands of DNA or of DNA and RNA.

hybridoma

cloned cell line made by fusing a short-lived functional lymphocyte with a cancerous cell of the same lineage to generate immortal functional cells. Fusion of a plasma cell producing antibody and a myeloma cell (cancerous plasma cell) forms a hybridoma which produces monoclonal antibody. T cell hybridomas can be made by fusing a helper or cytotoxic T cell with a cancerous T cell; these hybridomas secrete cytokines or are able to lyse target cells.

hyper IgM syndrome

immune deficiency in which serum IgM levels are high and serum IgG is absent or very low.

hyperacute graft rejection

graft rejection caused by pre-formed antibodies to antigens on the graft.

hypersensitivity

inappropriate immune response that damages one's body. Hypersensitivity responses are directed against non-dangerous antigens (allergens or grafts) or against persistent pathogens (Lyme arthritis).

hypervariable region

the region of antibody or TCR that specifically binds antigen.

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I

ICAM

InterCellular Adhesion Molecule, adhesion molecule that allows prolonged cell-cell contact during leukocyte activation or migration.

IDDM

Insulin-Dependent Diabetes Mellitus; Type I diabetes, and autoimmune disease.

idiopathic hemochromatosis

excessive iron absorption and deposition in the skin and tissues; idiopathic means the cause is unknown.

idiotype

the antigenic specificity of the variable (antigen-binding) region of an antibody or TCR molecule.

IFNa

alpha interferon; cytokine produced in response to virus infection that interferes with virus replication.

IFNb

beta interferon; cytokine produced in response to virus infection that interferes with virus replication.

IFNg

gamma interferon; cytokine produced by T cells that signals APC to express more membrane MHC.

Iga /Igb

Ig alpha-Ig beta. Signal transduction part of the B cell receptor complex.

Ig domain

globular fold in antibody and Ig superfamily molecules held in place by a disulfide bond.

Ig isotype

class of antibody molecules which share a heavy chain Fc region. There are five Ig isotypes: a (IgA), g (IgG) , d (IgD), e (IgE), and m (IgM).

Ig superfamily

group of proteins with structures very similar to Ig domains. Includes antibody, TCR, several receptors for cytokines, and some adhesion molecules.

immune complex

non-covalently bound complex of antibody with antigen and sometimes complement.

immune deficiency

congenital or acquired inability of the immune system to function correctly, usually due to lack of a molecule or cell.

immune surveillance

the constant process by which the immune system kills arising cancer cells.

immunoblot

Western blot or dot blot; detection of proteins on nitrocellulose paper by binding of labeled antibody molecules.

immunoelectron microscopy

detection of cell-associated molecules in the electron microscope with antibodies labeled with electron dense metals (often gold).

immunoelectrophoresis

detection of proteins which have been separated by electrophoresis by adding antibodies to form a visible precipitate in the gel.

immunofluorescence

detection of cell-associated molecules in the light microscope with antibodies labeled with fluorochromes.

immunogen

any molecule which can induce an immune response.

immunoglobulin

antibody, serum protein that binds antigen and facilitates its removal.

immunohistochemistry

detection of cell-associated molecules in the light microscope with antibodies labeled with enzymes which change a substrate into a colored precipitate.

immunophilin

cytoplasmic proteins in T cells which are the targets of the immunosuppressant drugs cyclosoprin A, FK506, and rapamycin.

immunotoxin

genetically engineered monoclonal antibody specific for a tumor cell. The Fc region has been modified or replaced with a toxin (such as ricin) which kills the tumor cell following antibody binding.

inactivated vaccine

vaccine composed of killed pathogen.

inbred mice

mice which are the progeny of many generations of brother-sister matings, so that they are homozygous for most genes. These syngeneic mice will accept skin and organ grafts from each other.

inflammation

defense to tissue injury; may be caused by the immune system. Inflammation includes movement of blood and leukocytes into the injured area.

inflammatory T cell

Th1 cell, which activates macrophages to kill vesicular pathogens.

innate immunity

immunity present from birth and not dependent on prior antigen exposure. Innate immunity includes physical and chemical barriers to infection, phagocytes, complement, and Natural Killer cells.

inositol triphosphate

second messenger in lymphocyte activation; increases intracellular calcium and activates calcineurin.

in situ hybridization

DNA-DNA or RNA-DNA hybridization done on whole cells which have been fixed to a surface such as a filter or microscope slide.

integrin

family of membrane adhesion molecules.

interdigitating dendritic cells

leukocytes with long processes (dendrites) that present antigen to T cells.

interleukin

a cytokine produced by one leukocyte and acting on another.

intron

non-coding region of a gene; DNA which is not expressed in the protein sequence. May be important for regulating gene expression.

ISCOM

ImmunoStimulating Complex. Lipid bilayer spheres containing antigen; designed to allow antigen to enter cells and by presented on class I MHC.

isotype

class of antibody molecules which share a heavy chain Fc region. There are five Ig isotypes: a (IgA), g (IgG) , d (IgD), e (IgE), and m (IgM).

isotype switch

the process by which a B cell switches from making antibody of one isotype to another without altering the specificity of the antibody.

ITAM

Immunoreceptor Tyrosine-based Activation Motif. Amino acid sequence in the cytoplasmic tail of receptor complex proteins which become phosphorylated during activation of cell function.

ITIM

Immunoreceptor Tyrosine-based Inhibition Motif. Amino acid sequence in the cytoplasmic tail of receptor complex proteins which are modified during inhibition of cell function.

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J

J chain

polypeptide chain found in IgM and IgA. Helps hold subunits of the polyvalent Ig molecules together and binds to receptor on mucosal endothelium for secretion.

junctional diversity

diversity in Ig or TCR structure generated by the inexact splicing of gene segments into a complete gene for Ig or TCR chains during B cell or T cell development.

K

K cell

Killer cell. Macrophage, neutrophil, or NK cell which uses Fc receptor to bind antibody-coated target cell and then kills the target.

killed vaccine

vaccine composed of killed pathogen.

killer inhibitory receptors

receptors for MHC on NK cells which block NK cell killing of self cells.

knock-out mice

mice in which one particular gene has been inactivated; used to study gene function by looking at the effects of its absence.

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L

LAK

Lymphokine-Activated Killer cell. Natural killer cell which has been activated by IL-2 to become cytotoxic.

late phase response

part of Type I hypersensitivity which requires protein synthesis and occurs several hours after the immediate histamine release.

leukocyte

white blood cell: neutrophil, basophil, eosinophil, or lymphocyte.

leukocyte adhesion deficiency (LAD)

immune deficiency in which one or more adhesion molecules are not expressed.

library

collection of DNA (genomic) or cDNA sequences within plasmid or virus vectors.

ligand

molecule which specifically binds a receptor and triggers a response from the cell. Antigen is the ligand for the mIg on B lymphocytes and triggers B cell immune responses; insulin is the ligand for insulin receptor and triggers glucose uptake.

limit(ing) dilution

a technique used to count the number of functional cells in a population.

LMP

Low Molecular weight Protein. Subunit of the proteasome, where endogenous proteins are processed.

LPS

LipoPolySaccharide; endotoxin. Present in the outer membrane of Gram negative bacteria.

lymphatic

vessel which transports lymph and leukocytes into and out of the lymph nodes and back into the circulatory system at the vena cava.

lymphocyte

leukocyte which has specific receptors for antigen and participates in adaptive immunity.

lymphoid progenitor

precursor to both T and B lymphocytes.

lymphokine

cytokine produced by a lymphocyte.

lymphokine-activated killer cell

Natural killer cell which has been activated by IL-2 to become cytotoxic.

lymph node

collections of lymphoid tissue distributed throughout the body, connected by lymphatics to the circulatory system. Antigen is taken to the lymph nodes and lymphocytes are activated there to effector cells.

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M

 
MIIC vesicle

cytoplasmic vesicle in antigen-presenting cells where class II MHC binds processed exogenous antigen.

mAb

monoclonal antibody; antibody produced from a clone of B cells.

MAC

Membrane Attack Complex; complement proteins which form a pore leading to cell lysis.

Mac-1

surface marker on macrophages.

macrophage

phagocytic white blood cell found in the tissues; the circulating form of the cell is called a monocyte. Acts as an antigen-presenting cell.

MAdCAM-1

adhesion molecule on mucosal cells; binds L-selectin and VLA-4.

MAGE

tumor antigen found on melanoma cells and also normal cells in the testis.

MALT

Mucosal-Associated Lymphoid Tissue; collections of lymphoid cells found along the mucus membranes of the respiratory, digestive, and urogenital tracts.

MBL

Mannan-Binding Lectin (mannose-binding protein). Acute phase protein which opsonizes pathogen and activates complement.

M cell

specialized antigen-collecting cell in the intestinal tract mucosal epithelium.

MCP

Macrophage Chemoattractant and activating Protein; a chemokine.

membrane attack complex

complement proteins which form a pore leading to cell lysis.

memory cell

lymphocyte which can respond more quickly and efficiently to antigen than a naive lymphocyte.

memory response

repeat response to an antigen which is faster and larger than a primary response.

MHC

Major Histocompatibility Complex; refers to the proteins used to present antigen to T cells or the genes which encode them. MHC proteins on body tissues must be matched between organ donor and recipient for an organ transplant to avoid rejection.

MHC restriction

the requirement for T cells to see antigen on self MHC.

minor histocompatibility antigen

tissue antigens besides MHC which are involved in graft rejection, usually to a lesser extent.

MIP

Macrophage Inflammatory Protein, a chemokine.

mitogen

molecule which induces proliferation (mitosis).

mixed lymphocyte reaction

tissue-typing test for transplantation. T cells from the recipient are mixed with APC from the donor; if foreign MHC molecules are present on the APC, the T cells proliferate and incorporate 3H- thymidine.

molecular mimicry

molecular similarities between foreign and self antigen which may lead to autoimmunity.

monoclonal antibody

antibody that is homogenous, every molecule identical to the next in physical structure and antigen binding; produced by a hybridoma.

monocyte

white blood cell with a single (non-lobed) nucleus; lymphocytes and the circulating form of macrophages are monocytes.

monokine

cytokine made by a monocyte.

mRNA

messenger RNA, template for protein synthesis.

multiple myeloma

plasma cell tumor, often characterized by high levels of monoclonal antibody in the circulation.

myeloma protein

the monoclonal antibody produced by myeloma cells.

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N

negative selection

the process of eliminating unwanted cells, often by killing them. Refers to the elimination of self-specific T and B cells during lymphocyte development or to the in vitro elimination of particular cells (for example, by incubating them with specific antibody plus complement).

neutrophil

white blood cell, a granulocyte that stains with neutral dyes. The most numerous of the circulating granulocytes, phagocytoses and kills bacteria.

NK cell

Natural Killer Cell.

Northern blotting
process used to identify mRNA with a particular nucleotide sequence. RNA is cleaved by restriction endonucleases, separated by gel electrophoresis, and blotted onto nitrocellulose paper. A probe of radioactively labeled RNA or DNA is incubated with the blot under conditions where it will hybridize with a complementary sequence.
NO

nitrous oxide, used by neutrophils and macrophages to kill pathogens.

nude mice

mice with an epithelial cell defect which results in hairlessness and also lack of a thymus.

O

opsonin

molecule which coats a pathogen and promotes its phagocytosis: antibody, complement, and MBL are opsonins.

oxidative burst

chemical process yielding toxic oxygen radicals and peroxides.

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P

PAGE

PolyAcrylamide Gel Electrophoresis, a technique for separating proteins by size using an electric current.

passive immunization

immunization using pre-formed antibody from another individual.

pathogen
disease-causing organism.
pathogenesis
the process of causing disease.
PBMC

Peripheral Blood Mononuclear Cell (lymphocyte or monocyte)

PBML

Peripheral Blood Mononuclear Leukocyte

peptidoglycan

bacterial cell wall material

perforin

molecule used by NK cells and cytotoxic T cells (CTL) to make pores in the membranes of target cells.

peripheral lymphoid organ

organs where lymphocytes are exposed to antigen: lymph nodes and spleen.

Peyers patch

lymphoid tissue in the peritoneal cavity, associated with the digestive tract.

phagocyte

cell which engulfs particles: macrophages and neutrophils are the principal phagocytes of the immune system.

phagocytosis

process of engulfing particle.

phagosome

cytoplasmic vesicle containing the engulfed particle.

phenotype

genetic characteristics expressed by the cell or organism.

plasma

fluid part of the blood, containing all proteins including clotting factors.

plasmid

piece of circular bacterial DNA, separate from the chromosome, which carries genetic information and is copied and inherited by daughter cells. Plasmids can be used as vectors to transfer DNA from one cell to another.

polymerase

DNA or RNA synthesizing enzyme

polymerase chain reaction (PCR)

technique for amplifying specific DNA sequences. Primers complementary to the ends of the DNA sequence to be copied are added to DNA polymerase and nucleotide bases; under repeated cycles of heating and cooling, multiple copies of the desired sequence are produced.

primary cell culture

cultured cells which recently came from an animal, plant, or person; not a clone and with a limited life span in culture.

probe

specific sequence of nucleotides, either RNA or DNA, radioactively labeled and used for identifying complementary sequences in Northern blotting (with mRNA) or Southern blotting (with DNA).

promoter

region of the DNA where RNA polymerase binds.

protease

protein cutting enzyme.

Phospholipase C

enzyme that cuts the membrane phospholipid phosphatidyl inositol into diacylglycerol (DAG) and inositol triphosphate (IP3).

plasma cell

white blood cell that synthesizes and secretes antibody.

pluripotent stem cell

hematopoietic stem cell that can give rise to all blood cells.

PMN

PolyMorphoNuclear leukocyte, a white blood cell with a lobed nucleus. Usually refers to a neutrophil.

polyclonal activation

activation of B cells or T cells with several different antigen specificities.

polyclonal antibody

antibody molecules with several different antigen-binding specificities.

positive selection

selection process that allows a cell to survive or persist in a mixed population. Lymphocytes must be positively selected during their development and activation to become effector cells.

pre B cell

a lymphocyte which has undergone H chain but not L chain somatic recombination.

pre B receptor

present on pre B cells; H chain with surrogate light chain (V pre B plus l5).

preTa

surrogate light chain on a pre T cell.

precipitation

becoming insoluble; an assay for antibody-antigen complexes.

primary lymphoid organ

lymphoid organ in which lymphocytes mature: bone marrow and thymus.

primary response

initial adaptive immune response to an antigen.

pro B cell

developing lymphocyte which has undergone D-J joining in the Ig gene region and expressed CD45 (B22) but had not yet become a pre B cell.

productive rearrangement

somatic recombination of BCR or TCR gene segments that results in synthesis and membrane expression of a functional (antigen-binding) receptor.

properdin

plasma regulator of alternative pathway complement function; stabilizes the C3bBb3b complex.

proteasome

cytoplasmic organelle which processes (cuts into peptides) cytoplasmic proteins for transport and display on membrane class I MHC.

protectin

CD59, a membrane inhibitor of complement membrane attack complex.

Protein Kinase C

second messenger in lymphocyte activation; cytoplasmic enzyme that phosphorylates and activates transcription factor NFkB.

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R

radiation chimera

an individual whose immune system has been destroyed by irradiation and replaced by hematopoietic stem cells from another individual. The name comes from the mythological beast which is part lion, part goat, and part snake (see chimera).

radioimmunoassay

assay for antigen-antibody binding which is detected using radioactive ligand.

RAG

Recombination Activating Gene(s). Gene(s) for the recombinase that is required for somatic recombination of both BCR and TCR genes.

RANTES

Regulation upon Activation Normal T cell Expressed and Secreted, a chemokine.

receptor

molecule which specifically binds a ligand; ligand binding triggers a specific response from the cell. Most receptors are on the cell's plasma membrane, but some can be cytoplasmic. Antigen is the ligand for the mIg on B lymphocytes and triggers B cell immune responses; insulin is the ligand for insulin receptor and triggers glucose uptake.

receptor editing

"second" chance somatic recombination events, usually on L or a chain gene segments to produce a functional BCR or TCR.

recombinant DNA

DNA composed of DNA from more than one source; for example, bacterial gene(s) in a virus genome.

recombinant vaccine

vaccine made by putting desired pathogen genes into a vector.

recombinase

enzyme which catalyzes somatic recombination of BCR and TCR gene segments.

recombination signal sequence

DNA sequence that allows for correct recombinase joining of different gene segments.

reporter gene

gene whose protein product can be easily measured, usually by its enzymatic activity. Included with cloned DNA to demonstrate integration of DNA into a transformed cell.

restriction endonuclease

bacterial enzyme which cuts DNA at particular DNA sequence; several hundred have been isolated.

restriction mapping

technique using two or more restriction endonucleases separately and together to cut DNA into segments of different sizes, then separating segments by gel electrophoresis to determine the location of the restriction sequences in the DNA.

reverse transcriptase

DNA-synthesizing enzyme which uses an RNA template.

reverse transcriptase

enzyme that transcribes RNA into complementary DNA.

Rh antigen

Rhesus antigen, protein antigen on erythrocytes.

Rhogam

human antibody to Rh antigen given to women to prevent hemolytic disease of the newborn.

rheumatoid factor

IgM anti-IgG, found in the serum of individuals with rheumatoid arthritis.

RIA

Radio Immuno Assay; assay for antigen-antibody binding which is detected using radioactive ligand.

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S

SCID mice

mice with Severe Combined Immune Deficiency resulting from the failure to develop mature T and B lymphocytes; suitable for adoptive transfer experiments in which their immune systems can be restored with normal cells.

SCID-human mice

SCID mice in which the immune system has been restored with human cells, so they have mature human B and T cells; used for the study of human lymphoid development and AIDS.

second messenger

usually an enzyme which is activated by ligand binding to receptor and transmits the ligand signal into the cytoplasm (and eventually the nucleus) to alter cell function.

secondary lymphoid organ

lymphoid organ in which lymphocytes are activated by antigen and accessory cells and become effector cells and memory cells. Includes the lymph nodes, spleen, mucosal lymphoid tissue, and bone marrow.

secondary response

repeat immune response to an antigen; memory response.

secretory component

protein on secretory Ig A which protects it from protease digestion

secretory IgA

IgA which is secreted from mucosal epithelial cells in the digestive, respiratory, and genital tract. Secretory IgA has an additional protein (secretory component) which protects it from protease digestion.

selectin

adhesion molecule which binds to carbohydrates. For example, L-selectin on lymphocytes binds to carbohydrates in the secondary lymphoid organs and allows the lymphocytes to leave the circulation and enter the lymphoid tissue.

self antigen

antigen normally present in one's own body, especially that with which the immune system has contact.

sensitization

initial contact with an allergen that results in IgE production and binding to mast cells, so that subsequent contact leads to rapid allergic symptoms.

septic shock

shock caused by immune response to infection.

serotype

antigenic specificity of a pathogen.

serum

liquid part of the blood minus the clotting factors.

shock

usually refers to low blood volume which can lead to death.

signal transduction

enzymatic cascade which follows ligand binding to receptor and results in change in cell function.

single positive T cell

T cell with either CD4 or CD8 on its membrane.

somatic hypermutation

mutation occurring preferentially in the V region of Ig genes during B cell clonal proliferation.

somatic recombination

process of cutting and splicing DNA segments to produce functional BCR or TCR genes.

Southern blotting

process used to identify specific pieces of DNA carrying a particular sequence. DNA is cleaved by restriction endonucleases and separated by gel electrophoresis, and blotted onto nitrocellulose paper. A probe of radioactively labeled RNA or DNA is incubated with the blot under conditions where it will hybridize with a complementary sequence.

stem cell

cell which can develop into more mature functional cells.

subunit vaccine

vaccine in which only parts of the antigen or pathogen are administered.

superantigen

antigen which binds TCR Vb and class II MHC outside the normal binding site and activates many different clones of T cells.

suppressor T cell

T cell which inhibits the function of B cells or other T cells.

surrogate alpha chain

alpha chain produced in pre T cells. Used to positively select pre T cells which have successfully undergone somatic recombination of b chain for further development.

surrogate light chain

light chain produced in pre B cells. Used to positively select pre B cells which have successfully undergone somatic recombination of L chain for further development.

switch region sequence

DNA sequence that allows a plasma cell to recombine V region DNA with a different C region.

syncytia

multi-nucleate cells formed when cells fuse their plasma membranes.

syngeneic

homozygous at >98% of genes; see inbred mice.

systemic lupus erythematosis

systemic autoimmune disease characterized by facial rash (wolf-like markings, hence "lupus"), high levels of anti-DNA antibodies, and joint and kidney damage from immune complexes.

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T

T cell

lymphocyte which has developed in the thymus and has membrane TCR that binds antigen plus self MHC. T cells are either helper (CD4) or cytotoxic (CD8) phenotype.

T cell activation

biochemical process of stimulating a resting T cell to become an effector cell.

T cell development

development of T cells in the thymus.

T cell education

selection of T cells which can bind self MHC with appropriate affinity to be MHC-restricted.

T-dependent antigen

antigen which generates T cell help for B cells.

T-independent antigen

antigen which stimulates B cell directly, without T cell help.

TAP

Transporter of Antigen Peptide; protein complex that moves peptides from the cytoplasm into the endoplasmic reticulum where that can bind class I MHC.

tapasin

chaperone in the endoplasmic reticulum which facilitates peptide loading onto class I MHC.

target cell

cell to be lysed by a cytotoxic cell; usually a virus-infected cell, for ADCC an antibody-coated cell.

TCR

T cell (antigen) receptor, membrane molecule that binds antigen peptide plus MHC.

template

instructions for synthesis; mRNA is synthesized from a DNA template by an RNA polymerase which reads the DNA sequence and inserts complementary RNA bases.

TGFb

Tumor Growth Factor beta, a cytokine made by T cells and monocytes.

Th1 cell

helper T cell that activates macrophages and cytotoxic T cells.

Th2 cell

helper T cell that activates B cells.

thymocyte

cell which resides in the thymus

thymus

primary lymphoid organ in which T lymphocytes mature

TIL
Tumor-Infiltrating Lymphocyte, lymphocytes (usually T and NK cells) which enter tumor in an attempt to kill tumor cells.
titer

quantification of antibody, often expressed as the highest dilution to give a positive response.

TNFa

Tumor-Necrosis Factor alpha, a cytokine made by macrophages, mast cells and NK cells.

TNFb

Tumor-Necrosis Factor beta, a cytokine made by T cells.

tolerance

the inability of the immune system to respond to an antigen.

tonsils

lymphoid tissue in the throat.

toxoid

inactivated toxin, often used as a vaccine against the toxin.

transcription

synthesis of mRNA from DNA template.

transfection

transfer of foreign DNA into a cell.

transformation

transfer of a recombinant plasmid vector into a bacterial cell, or conversion of a normal cell into a cancer cell.

transgene

cloned foreign gene inserted into a cell.

transgenic mice

mice which have a foreign gene in their cells. Since the gene is inserted into a fertilized egg, it is present in all cells of the mouse but may not be expressed in all cells.

translation

synthesis of protein from messenger RNA (mRNA)

trypan blue

dye which can enter dead cells, used for determining viability.

TSST

Toxic Shock Syndrome Toxin, a super antigen produced by Staphylococcus aureus that causes toxic shock syndrome.

tumor immunology

subspecialty of immunology dealing with immune responses to tumors.

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U

urticaria

also called hives: small areas of local inflammation in the skin.

V

vaccine

antigen used for deliberate exposure and induction of protective immunity.

vascular addressin

cell adhesion molecule (CAM) on vascular endothelium.

vascular endothelium

endothelial cells lining the blood vessels.

VCAM

Vascular Cell Adhesion Molecule, CAM found on the endothelial cells lining blood vessels.

vector

autonomously replicating DNA molecule which can be used to clone and move inserted DNA from cell to cell. Commonly used vectors are viruses and bacterial plasmids.

viability stain

stain that differentiates between live and dead cells.

vitronectin

plasma protein (also called S protein) that block binding of complement C567.

VpreB

part of the surrogate light chain on pre B cells.

W

Western blot

polyacrylamide gel electrophoresis of proteins followed by blotting and, binding of enzyme-tagged specific antibodies; used to detect specific antigens.

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X

X-SCID

X-linked Severe Combined Immune Deficiency, due to defect in IL-2 receptor g chain.

xenograft

organ graft from another species

xenotransplantation

transplantation of tissue from another species

XLA

X-Linked Agammglobulinemia, an immune deficiency caused by lack of Bruton's thymidine kinase and resulting in recurring infections due to nearly complete absence of serum Ig.

Z

ZAP-70
tyrosine kinase second messenger in T cell activation.

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http://microvet.arizona.edu/Courses/MIC419/ToolBox/glossary.html
Written by Janet M. Decker, PhD       jdecker@u.arizona.edu
Last modified June 9, 2003