Role of monocytes/macrophages and interleukin 1 in antigen-induced human lymphokine production.

The monocyte/macrophage (M phi)-dependency for antigen-induced production of the lymphokine, leukocyte migration inhibitory factor (LIF), was investigated using a M phi pulse-exposure technique. M phi-depleted, purified T lymphocytes did not elaborate LIF in response to the recall antigen, tuberculin (PPD). Addition of M phi's pulsed with PPD rectified the response. Exposure of the M phi's down to 3 min, even at 0 degree C, was efficacious. PPD-exposed M phi's, either killed or rendered incapable of protein synthesis, failed to activate the T cells. However, PPD-exposed, killed M phi's triggered LIF production if exogenous interleukin 1 (IL-1) was provided. We suggest that M phi "presentation" of antigen in this test system is a passive albeit necessary, process; the requirement for M phi metabolism being confined to the elaboration of IL-1. Judged by the results of kinetic experiments, the latter stimulus appears to be mediated most effectively from 2 to 4 hr after antigenic challenge.