Possible Autoregulatory Roles of Interleukin 1 for Normal Human Epithelial Cells, Monocytes and B Lymphocytes

Of all the hormones and growth factors that have been tested only interleukin 1 and 2 (IL 1 and 2) have been documented to be costimulants of thymocyte proliferation. Consequently the operational definition of IL 1 is that of a comitogenic factor for thymocytes that, in contrast with IL 2, does not support the growth of IL 2 dependent lymphocyte cell lines. Another difference between these two cytokines is that IL 2 is produced only by T lymphocytes and some large granular lymphocytes (LGL) (1), whereas IL 1 is produced by many types of cells including monocyte/ macrophages, LGL, keratinocytes, mesangial cells of the kidney, astrocytes, some EBV transformed B cell lines fibroblasts, melanoma cell lines, endothelial cells, and glioma cell lines (as reviewed in 2). Although some of the IL 1 activities derived from non-macrophage cell sources have been partially purified, their precise relationship to macrophage-derived IL 1 will be clarified only when their amino acid sequences become known.