Term
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Definition
| subset of antigens actually able to induce an immune response; the immunogenecity of an Ag is determined by the induction of the innate arm with adjuvants, induction of adaptive immunity, and discrimination of self/nonself |
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Term
| what is the most common TCR heterodimer? |
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Definition
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Term
| which Ig domain is variable? |
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Definition
| the VH & VL, which are the initial loops closest to the N terminus of the Ig protein |
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Term
| what connects Fc and Fab? |
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Definition
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Term
| what region of receptor binds antigen? |
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Definition
| CDR, the concentrated areas of genetic variability (short amino acid sequences/loops). There are 12 CDRs/per non-IgM immunoglobulin (3 CDRs/chain). The CDRs are located in the VL and VH of the Ig. CDR1, 2, and 3. |
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Term
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Definition
| in the variable region of the Ig, but do not bind antigen. help in maintaining structure. each chain has 4 FWRs and 3 CDRs |
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Term
| what molecules enable signal transduction? |
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Definition
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Term
| why are hinge regions so important? |
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Definition
| enable the Ig to bind to multiple repetitive epitopes in different configurations, bc they can stretch apart or close together, as needed |
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Term
| what does the aB-TCR bind? |
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Definition
| a composite antigen: a peptide fragment bound to MHC proteins; may only bind linear peptide antigens |
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Term
| describe structure of TCR chains |
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Definition
| each chain contains 1 variable and 1 constant domain; V domain binds antigen, and C domain anchors TCR to membrane |
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Term
| what is neutralization and what Abs mediate it? |
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Definition
| neutralization is the Ab binding of microbe/toxin to prevent its entry/infection of cells and tissues. IgA, IgG, IgM are all involved in neutralization |
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Term
| which Fc receptor is inhibitory? |
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Definition
| Fc-gamma-IIB receptor has an ITIM |
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Term
| what Ig is the most potent activator of complement? |
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Definition
| IgM (due to its pentamer status) |
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Term
| how is mucosal transport of IgA mediated? |
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Definition
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Term
| what produces IgA and the J chain? |
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Definition
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Term
| what produces the poly-Ig receptor? |
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Definition
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Term
| what purpose does the J chain? |
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Definition
| every Ab produced by B cells, associates with a J chain; most likely necessary for mucosal secretion, since IgA dimerizes before binding with poly-Ig receptor |
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Term
| how does IgA get into lumen? |
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Definition
| travels with poly-Ig receptor inside mucosal epithelial cell; after a proteolytic cleavage, the poly-IgR/IgA complex exits into lumen |
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Term
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Definition
| neonatal FcR; fetal and neonatal transport of IG is mediated by the FCRn |
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Term
| why is IgM always the first Ig produced? |
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Definition
| on chromosome 14, where all the genes for the 9 isotypes resides, the gene for IgM is the first one in the sequence, is therefore the first to be transcribed. |
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Term
| why can IgM and IgD be expressed simultaneously? |
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Definition
| the isotype choice between IgM and IgD (the second genes) is decided at the level of transcription via alternative splicing. as such, a B cell can express both simultaneously |
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Term
| how are all other istotypes generated? |
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Definition
| IgG, IgA, IgE are all produced via DNA recombination/isotype heavy chain switching |
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Term
| what is the purpose of the switch region? |
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Definition
| a DNA sequence located after the C(m) gene [Sm]and BEFORE each of the Cg [Sg], Ca [Sa], Ce [Se]--mediates the recombination by looping out the intervening DNA sequences, resulting in a permanenent switch of a C gene from one isotype to another |
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Term
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Definition
| activation-induced cytidine deaminase: a DNA deaminating enzyme ABSOLUTELY REQUIRED for BOTH class switching [constant domains] and somatic hypermutation [variable domains] |
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Term
| when does class switch occur? |
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Definition
| in the late stage of B cell development after antigen exposure, in response to various signals provided by t cells in the lymphoid follicles; mediated by cytokines that induce switching to particular isotypes |
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Term
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Definition
on NK cells; permits identification of target cell coated with Ab, tagged for killing; target cell is killed by cytotoxic compounds released by NK cell
IgG1, IgG3 mediate NK dependent ADCC |
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Term
| what Abs arecomplement-fixing? |
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Definition
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Term
| when does IgA present as a dimer? |
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Definition
in serum, IgA is a monomer
in secreted fluids and in mucosa, IgA is a dimer associated with the J chain (both produced by B cell that reside in the gut lamina propria, respiratory tract, and urogenital tract) |
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Term
| how is transport of IgG1 and IG3 mediated from mom into fetal circulation? |
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Definition
IgG1 and IgG3 across the placenta and neonatal intestinal epithelium into blood circulation is mediated by NEONATAL Fc RECEPTOR (FcRn).
in newborns, both maternal IgA and IgG are passed through breastmilk |
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