Interleukin 1 is more than an interleukin.

Gery and co-workers(1) first described lymphocyte activating factor (LAF) in 1972, as an activity produced by cultured human peripheral blood adherent leukocytes which was directly mitogenic for murine thymocytes but not for immunocompetent peripheral lymphocytes. Human LAF also synergistically augmented the mitogenic effects of the lectins ConA and PHA on murine thymocytes and splenic T lymphocytes(1). Since then LAF has been shown to promote lymphocyte differentiation and functions and even to affect a variety of nonlymphocytic larget cells. In view of the many biological activities attributed to this macrophage-derived factor, LAF was renamed 'interleukin 1' (IL 1) at the Second International Lymphokine Workshop at Ermatingen, Switzerland, in 1979(2). Partly as a consequence of the resultant controversy, this term has become widely known and will be used in this review, even though, as J. J. Oppenheim and Igal Gery show, IL 1 is more than a signal between leukocytes.