CH 7 Antibody 7E03
CH 7 Antibody 7E03
CH 7 Antibody 7E03
Q. A number of bacterial components enhance the expression of MHC molecules and co-stimulatory molecules on
macrophages. What effect would you expect this to have on
the immune response? Would it be advantageous for the
individual?
A. In the presence of infection, the action of the microbial
components would enhance the ability of macrophages to
present antigen to T cells. This would generally be advantageous because it would allow the immune system to respond
more effectively to the infection. However, in some circumstances it might be disadvantageous because microbial components would also enhance unwanted immune responses such
as autoimmune reactions.
B cells can:
bind to a specific antigen through surface IgM or IgD;
internalize it; and
then degrade it into peptides, which associate with
MHC class II molecules.
If antigen concentrations are very low, B cells with highaffinity antigen receptors (IgM or IgD) are the most
effective APC because other APCs simply cannot capture
enough antigen. Therefore, for secondary responses,
when the number of antigen-specific B cells is high, B cells
may be a major type of APC.
B cells do not normally express co-stimulatory molecules such as B7, but these can be induced by bacterial
constituents.
The properties and functions of some APCs are
summarized in Figs 7.3 and 7.4.
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