Therapy of secondary T-cell immunodeficiencies with biological substances and drugs.

Thymus-dependent (T) lymphocyte defects are common in cancer. Recent advances in the understanding of the regulation of T-cell development by biologicals and drugs now allow the formulation of better strategies of immune reconstitution to correct these defects. Thymic hormone preparations of several types offer one type of approach; however, they are somewhat limited in their reconstitutive ability. Interleukins (IL), particularly IL-1 and IL-2, appear to be complementary to the actions of thymic hormones in promoting T-cell development. Two classes of thymomimetic drugs have been identified and are represented by levamisole and isoprinosine. These drugs mimic by indirect and direct actions, respectively, the actions of thymic hormones. Newer analogs of these compounds have emerged which appear more effective. Also new factors, e.g. pituitary factors, are emerging which may be potent regulators of the immune system and useful in therapy. These agents may now be more effectively integrated with cytodestructive therapy in cancer treatment.