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13 Cards in this Set
- Front
- Back
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What is the importance of B-cells?
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Protects against extracell pathogens, goal of may vaccines, forms basis for humoral immunity
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Describe naïve B-cell.
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MHC II, CD40, IgM, IgD, & cytokine receptors.
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What is the diff b/w the antigens that B-cells & T-cells recog?
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B-cell recog intact Ag molec (conformational determinants), & T-cells recog peptide form of Ag (linear determinant); they recog diff epitopes
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Describe overall process of primary Ab response to thymus-dependent Ag.
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APC engulfs & process Ag-> APC activates T-cell while B-cell recog Ag by cross linking of membrane bound Ab (signal 1)-> CD4 helper T-cell activates B-cell-> isotype switching & affinity maturation-> plasma cell or memory cell
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What are the 2 fates of activated B-cells?
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Prolif: Some become plasma cells that secret low affinity IgM. Others undergo heavy chain isotype switching & affinity maturation->plasma cells that secrete IgG, A, & E & high affinity memory B-cells
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What is affinity maturation?
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B-cell secreting Ab of progressivelyhigher affinity are selected. Specificity is unchanged, reg by Ag concen, important in vaccination, occurs only in non-IgM B-cells
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Charac of class switching.
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Involves cleaving intervening DNA so it’s irreversible. Reg by T-cell & macro cytokines. Somewhat dependent on site immun: inhaled Ag promotes IgE & mucosal surfaces promote IgA
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Charac of secondary response to TD-Ag
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Shorter lag phase, extended plateau & decline. Higher Ab titers & affinity. Consistent primarily of (IgG w/ some IgM). Additional exposure to Ag inc Ab response & titers (reason for booster shots)
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What are thymus-independent Ag?
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Some bacterial Ag consisting of polysacc, LPS or polymeric proteins. Can stim B-cell Ab production w/ little T-cell help. Not in infants, no affinity maturation, no memory cells, no secondary repsonse.
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Describe TI Ab response.
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B-cell needs only 1 signal. Can trigger B-cell activation via toll-like receptors
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What are haptens?
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Small chemical group that is antigenic but is only immunogenic when liked to protein carrier. Recog by B-cells but not t-cells (eg penicillin). Haptenated peptides can be recog by T-cells.
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What is linked recog?
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Normally B & T-cell that interact to produce Ab are specific for the same Ag. But can get Ab production by T & B-cells of diff specificity if protein source of peptide recog by T-cell is linked to hapten or other protein recog by B-cell
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Clinical importance of linked recog.
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Used in the design of vaccines (eg Hemophilus Flu)
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