Interleukins and inhibitors in human lymphocyte regulation

It seems clear, from studies in many laboratories, that both IL-1 and IL-2 play an important role in lymphocyte activation and are thus significant in the initiation and amplification of an optimal immune response. These conclusions have been extended to human lymphocytes, and preliminary data with macrophages and T-cells from alveolar spaces suggest that the interleukins are also important in vivo. A number of details remain to be worked out concerning these complex cellular and humoral interactions involved in triggering the immune response, and the increasing availability of purified reagents should help to speed the clarification of remaining issues. To date, much less work has been done with inhibitory factors produced by macrophages and lymphocytes than with the stimulatory interleukins. The preliminary studies by our laboratory and by others suggest that some suppressive agents may act through interference with the IL-1-IL-2 pathway and that others may be interleukin independent. Such investigations are only beginning, however, and much more investigation is needed to dissect in detail the mechanisms by which immunologically nonspecific inhibitory factors may contribute to the regulation of early steps in the immune response.