Frequency and activity of immune interferon (IFN-gamma)- and colony-stimulating factor-producing human peripheral blood T lymphocytes.

This report describes the first frequency estimate of immune interferon (IFN-gamma)- and colony-stimulating factor (CSF)-producing human peripheral blood T lymphocytes. Human peripheral blood lymphocytes (HPBL) were activated with T cell mitogens [concanavalin A (Con A) or phytohemagglutinin (PHA)] in bulk culture and subsequently plated in limiting dilution (LD) microcultures in the presence of irradiated allogeneic HPBL filler cells and culture medium supplemented with human interleukin 2 and T cell mitogen (Con A or PHA). HPBL growing in these cultures were T cells as determined by E-rosetting (greater than 85%) and were positive for the OKT8 marker. The growth frequency (f) of HPBL in LD was f = 1/20-1/100. Such cells were induced with T cell mitogens (Con A or PHA) to release lymphokines into the supernatant. Statistical analysis of the data from the LD experiments showed that (a) the precursor cell frequency for IFN-gamma- and CSF-producing T cells was f = 1/63-1/151 and 1/89-1/217, respectively, and (b) most T cell clones released IFN-gamma and CSF simultaneously. In addition, individual T cell clones were shown to be capable of releasing different CSF types. In principle, this experimental system can be used to evaluate the precursor frequency, relationship and activity of normal or pathological human T cells performing any in vitro T cell function.