FcR+ and FcR- monocytes differentially secrete monokines during pokeweed mitogen-induced T-cell-monocyte interactions.

Monocyte subpopulations which differ in the expression of Fc receptor for human IgG (FcRI) differentially regulate the T-cell-dependent, pokeweed mitogen (PWM)-induced, polyclonal B-cell response. We, thus, studied the cytokine production in human peripheral blood monocyte and T-lymphocyte cultures activated with this lectin. Monocytes or their FcR+ and FcR- subpopulations stimulated with PWM were cultured with or without T lymphocytes or their CD4+ and CD8+ subsets. Both monocyte subpopulations cultured alone produced similar amounts of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), but FcR- monocytes showed significantly enhanced ability to secrete interleukin-1 (IL-1). T cells, especially CD4+, added to monocyte cultures enhanced IL-1 production. This enhancement was presumably due to interferon-gamma (IFN-gamma) release by T lymphocytes, since this lymphokine enhanced IL-1 secretion when added to PWM-stimulated cultures of monocytes. Addition of monocytes, in particular the FcR+ subpopulation, greatly enhanced production of IFN-gamma by T lymphocytes. Although both T-cell subsets produced IFN-gamma, the CD4+ cells were more efficient. These results indicate that in PWM-stimulated cultures subpopulations of monocytes differ in secretion of cytokines, which might explain their differential effect on T-cell-dependent immune responses in vitro.