Question 83

Question:

A 48-year-old man receives a liver transplant for end-stage alcoholic cirrhosis. Three weeks after the transplant surgery, the man experiences fevers, chills and fatigue related to an acute rejection of the transplant. The host cells involved in this response recognize foreign antigens presented by antigen presenting cells (APC). These antigens are presented to host cells on which of the following APC receptor types?

Correct Answer: E.  MHC Class II

Acute transplant rejection is a cytotoxic T-cell mediated process whereby cytotoxic T-cells (Tc) are indirectly activated by helper T cells (Th). Th possess a T-cell receptor (TCR) that interacts with MHC Class II antigen presenting receptors on APCs. B7 and CD28 costimulation is necessary for Th activation, but does not involve actual presentation of the antigen. IL-2, a cytokine secreted by activated Th cells, serves to stimulate growth of Th and Tc’s.