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15 Cards in this Set
- Front
- Back
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what are immunoglobulins (Ig)?
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* antigen-recognition molecules of B-cells
* produced by B-cells in vast range of antigen specificities (ie: membrane-bound Ig on B-cell surface serves cell's receptor BCR for antigen * Ig of the same antigen specificity is secreted as ANTIBODY by terminally differentiated B-cells (plasma cells) |
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what is antibodies?
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* first molecules involved in SPECIFIC immune recognition to be recognized
* secreted form of B-cell receptor * has 2 functions: 1. to bind specifically to molecules from pathogen that elicited immune response 2. to recruit other cells and molecules to destroy the pathogen once antibody is bound to it. |
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what are the variable region and constant region?
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VARIABLE (V) region:
* antigen-binding region varies extensively between antibody molecules CONSTANT (C) region: * region of the antibody molecule that engages the effector functions of the immune system does not vary in the same way * comes in 5 forms that specialized for activating different effector mechanisms * functions is to recognize and bind antigen by V-regions exposed on cell surface, hence transmitting signal that causes B-cell activation (leading to clonal expansion and specific antibody production) |
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what is an immunogen
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A substance that induces a specific immune response.
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what is an antigen (Ag)?
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A substance that reacts with the products of a specific immune response.
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Major Histocompatibility Complex (MHC)
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* glycoproteins (MHC molecules) encoded in large cluster on human chromosome 6 or mouse chromosome 17.
* encodes proteins involved in antigen processing and other aspect of host defense * most polymorphic gene cluster in the human genome (having large number of alleles at several different loci (specific location of a gene/ DNA sequence on chromosome) * aka: major histocompatibility antigens |
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MHC Class I
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* present antigenic peptides generated in the cytosol to CD8 Tcells
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MHC Class II
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* present antigenic peptides generated in the cytosol to CD4 Tcells
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MHC restriction
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refers to the fact that a given Tcell will recognize a peptide antigen only when it's bound to a particular MHC molecule
(antigen is recognized only when bound to self MHC molecules) |
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5 different classes of immunoglobulin (Ig), from the location of its C-region
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* IgM (has μ Heavy chain)
* IgD (has δ Heavy chain) * IgG (has γ Heavy chain) * IgA (has α Heavy chain) * IgE (has ε Heavy chain) |
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What is the structure of IgG antibodies like?
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* large molecules composed of 2 kinds of polypeptide chains:
-- (H)eavy chain -- (L)ight chain * Ea. IgG molecule consists of 2 H-chains (linked to ea.other by disulfide bonds) and 2 L-chains. Ea.L-chains is connected to an H-chain by a disulfide bond. * 2types of L-chains: lambda (λ) and kappa (κ) found in antibodies. A given Ig has either kappa/lambda, not one of each. * ratio of kappa:lambda in human is 2:1. Distortions in this ratio can be used to detect abnormality in proliferation of a clone of B-cells. * IgG has most abundant immunoglobulin (Ig) and has several subclasses. |
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Distinctive Features of Immunoglobulin Heavy and Light chains
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1. each chain consist of series of similar (not identical) sequences repeating correspondently to protein domain region
* L-chain is made of 2 Ig domains * H-chain of IgG contains 4 domains 2. amino terminal sequences of both H and L chains vary greatly between different Ab (antibodies) * amino-terminal variable domain (V domains) of H and L chains (VH and VL)together make up the V region of Ab and confer the ability to bind specific antigen * the Constant domains of the H and L chains (CH and CL) make up the C-region |
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More on the antibodies structure
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* when fully folded, Ab molecule comprises 3 equal sized globular portions joined by a flexible stretch of polypeptide chain (a hinge region)
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what is FAB Fragments
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= Fragment Antigen Binding
= an antibody (Ab) molecule cleaved by papain consist of a single arm of the Ab composed of Lchain and the amino-terminal half of a Hchain held together by an interchaib disulfide bond * corresponds to the 2identical arms of the Ab molecule, ea. consist of a complete L-chain paired with VH and CH1 domains of a H-chain |
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FAB2 Fragment
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produce of an enzyme pepsin cleaves an antibody molecule, where 2 arms of the Ab molecule remain linked
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