Which One of the Following Statements About T Cell Tolerance

Multiple Choice

Which one of the following statements about T cell tolerance to self proteins is accurate?

A) Self proteins are not presented by the class I pathway because only microbial proteins,and not self proteins,are ubiquinated in the cytosol.
B) Peptides derived from self proteins are not presented by the class I or class II pathways because MHC molecules are expressed only in response to infections.
C) Self proteins are not presented by the class II pathway because endosomal acidic proteases digest microbial proteins but not eukaryotic proteins.
D) Self peptide/self MHC complexes are formed and displayed by antigen-presenting cells in both class I and class II MHC pathways,but T cells that recognize these complexes usually are not present or are functionally inactive.
E) Peptides derived from self proteins are not displayed by MHC molecules because they usually are displaced by the more abundant microbial peptides.