Serum inhibitors of interleukin-2.

Interleukin-2 (IL-2) is an important modulator of cell-mediated immunity. Its activity is suppressed by various serum inhibitors generated under normal and pathological conditions. It is believed that an inhibitor which occurs in normal serum is a T-cell derived heat labile protein (or protein-glycolipid complex), and it acts in a homeostatic mechanism to restrict IL-2 action to the vicinity of the activated T cells. Changes in inhibitory activity have been found in various physiological and pathological states, e.g. during ontogeny, in systemic lupus erythematosus, in rheumatoid arthritis, and with some systemic infections. There are also suggestions that some tumor cells generate IL-2 inhibitors which diminish killer cell activity against the tumor. It is possible that a better understanding of IL-2 inhibitors would help elucidate some pathological mechanisms connected with disturbed cellular immune responses.