Which of the following statements about the antigen-presenting function of macrophages is NOT correct?
A)Macrophages are particularly important at presenting peptides derived from particulate or opsonized antigens that are internalized by phagocytosis.
B)Macrophages become activated by the helper T cells to which they present microbial peptides,and as a result of this activation they become efficient at killing the microbes.
C)Resting macrophages express low levels of class II MHC molecules,but higher class II MHC expression is induced on activation by the T cells to which they present antigen.
D)Macrophages express highly variable,high-affinity receptors for many different antigens,and these receptors facilitate the internalization of the antigens for processing and presentation.
E)Macrophages present antigen to T cells in lymphoid organs and many nonlymphoid organs.

Question

Quizplus · Accepted Answer

The description of high-affinity and highly variable receptors for antigen applies to B cells,which can present antigen to helper T cells,but does not apply to macrophages.Macrophages express receptors for the Fc region of Ig molecules,and these receptors do facilitate internalization of antibody-opsonized antigens.These Fc receptors are not highly variable and do not recognize the antigen.Macrophages are also highly competent at internalizing intact microbes and other large particulate antigens through phagocytosis.Macrophage class II MHC expression and microbicidal activity are enhanced by signals from the T cells to which they present antigen,including cytokines and CD40 ligand.Macrophages are abundant in spleen,lymph nodes,and most nonlymphoid tissues.They may perform antigen-presenting functions in all these locations.

Which of the Following Statements About the Antigen-Presenting Function of Macrophages