Production of human immune interferon (Hu IFN‐γ) studied at the single cell level. Origin, evidence for spontaneous secretion and effect of cyclosporin A

Abstract A reverse hemolytic plaque assay has been developed which specifically detects secretion of human immune interferon (Hu IFN‐γ) at the single cell level. Unstimulated peripheral blood lymphocytes from healthy adult volunteeers spontaneously secreted IFN‐γ. Stimulation of these cells with concanavalin A, phytohemagglutinin, or the UCHT1 monoclonal anti‐human T cell antibody significantly increased the number of IFN‐γ‐secreting cells. The cell producing IFN‐γ, both spontaneously and after UCHT1 antibody stimulation, is an OKT3 + , 4 + ,8 − ,HLA‐DR − T lymphocyte as determined at the single cell level. Finally, cyclosporin A, a potent and selective immunosuppressive drug for T cells, strongly inhibited the secretion of IFN‐γ as assayed at the cell level. This IFN‐γ reverse hemolytic plaque assay has great potential for the further study of IFN‐γ both in physiological and pathological conditions.