The most common types of immunosuppressive agents used clinically include which of the following?

A. Antimetabolites.

B. Alkylating agents.

C. Inhibitors of helper T-cell activation.

D. Irradiation.

E. Lymphocyte depletion compounds.

DISCUSSION: Much of the susceptibility of lymphocytes to immunosuppression is due to the vast cellular changes that follow immune stimulation. The biosynthetic events that take place make the lymphocytes vulnerable to inhibition at various stages of the cell cycle. Cyclosporine inhibits cytokine gene expression, whereas alkylating agents and radiation produce cross-linkages and breaks in DNA strands that interfere with cell differentiation and division. Agents that produce depletion of lymphocytes include antilymphocyte globulin (ALG) and monoclonal antibodies (OKT3).