Which of the following characterize the role of the major histocompatibility antigens in immune responses?

A. The major histocompatibility antigens are critical in antigen processing and presentation.

B. Major histocompatibility antigens contribute to the maturation of T cells in the thymus.

C. T cells recognize only foreign antigens that are complexed with major histocompatibility antigens.

D. Expression of major histocompatibility antigens is increased in inflammation.

E. Recognition of major histocompatibility antigens is critical to the development of tolerance. 

DISCUSSION: Once thought to be solely markers of individuality, MHC antigens are crucial to cell-mediated immune responses. Foreign antigens taken up by antigen-presenting cells are degraded and then become complexed with MHC molecules and expressed on the cell surface, and these events are enhanced in inflammation. Since T cells recognize only foreign antigens expressed as peptides in association with MHC antigens, the possibility for recognition is increased as a consequence of inflammation. Since T cells recognize only antigens expressed in association with MHC antigens, recognition of these antigens is critical to the development of tolerance to “self.”