CYTOKINE PRODUCTION BY HIGHLY PURIFIED HUMAN CD8+T CELLS

We have systematically investigated the capacity of highly purified hu man peripheral CD8+ T cells to produce interleukin (IL)-4 and interfer on (IFN)-gamma, when triggered by different stimuli. CD8+ T cells were isolated from peripheral blood by positive selection to > 99% purity and stimulated with one of three different stimuli: phytohaemagglutini n (PHA) and IL-2, phorbol myristate acetate (PMA) and ionomycin, and p late-bound anti CD3 and PMA. On their own, ionomycin and IL-2 failed t o stimulate significant CD8+ T cell proliferation while PHA, plate-bou nd anti-CD3 and PMA induced weak proliferation. A combination of PHA a nd IL-2, PMA and ionomycin, or plate-bound anti-CD3 and PMA all induce d vigorous CD8+ T cell proliferation. IFN-gamma was produced following all three stimuli, but was greatest from cells cultured with PMA and ionomycin. However, IL-4 secretion was only detected in cell cultures stimulated with PMA and ionomycin. These results indicate that, with s ufficient stimulation, human CD8+ T cells have the potential to produc e Th2 as well as Th1 cytokines.