Which of the following is/are true of the antiproliferative agents?

A. They act by preventing the differentiation and division of the immunocompetent lymphocyte after it encounters antigen.

B. The antimetabolites in this group have a structural similarity to cell metabolites and either inhibit enzymes of a metabolic pathway or are incorporated during synthesis to produce faulty molecules.

C. The most frequently used antiproliferative agent is azathioprine. 

DISCUSSION: Antiproliferative agents inhibit the full expression of the immune response by preventing the differentiation of the immunocompetent lymphocyte after it encounters antigen. They act in one of two ways: they either structurally resemble necessary metabolites, or they combine with certain cellular components, such as DNA, and thereby interfere with function. Until recently, azathioprine was the most widely used immunosuppressive drug in transplantation, and it still has a major clinical role in preventing rejection.