Heterogeneity of soluble T cell products I. Precursor frequency and correlation analysis of cytotoxic and immune interferon (IFN-γ)-producing spleen cells in the mouse

In this study, the precursor frequency, relationship and activity of murine splenic cytotoxic and immune interferon (IFN-γ)-producing cells has been determined. C57BL/6 spleen cells were activated by concanavalin A (Con A) and subsequently grown in microcultures under limiting dilution conditions. The progeny of cells plated in microcultures was divided and tested for (a) total cytotoxic activity on EL4 (H-2b) tumor target cells in the presence of Con A to nonspecifically attach the killer to the target cells, and (b) the quantity of IFN-γ released by Con A stimulation. Cytotoxic T lymphocytes and IFN-γ producing cells were present in Con A-activated C57BLi6 spleen cells at a high frequency of approximately 1 out of 3 and 1 out of 2 cells, respectively. IFN-γ could be released from both noncytotoxic and a large fraction of cytotoxic T cells and the cytotoxic activity was not necessarily associated with IFN-γ release. In a few selected cultures with a progeny of cells plated at a low cell number (up to 10/well) very high IFN-γ titers (> 10000 U/ml) could be found. These results provide the first frequency estimate of IFN-producing cells and are discussed with respect to the physiological role of IFN-γ release from T cells.