[The regulation of the activation of cytotoxic lymphocytes may be mediated by a lymphokine]

Abstract

MLC-CML reactivity declines after approximately the 7th day of culture. The experiments described were designed to probe the reason for this decline, envisaged as due to the signals (SD or LD determinants) required for CML activation. Either fresh stimulating cells or a lymphokine--blastogenic factor (BF)--were added daily to mixed cultures from the 5th to the 12th day of incubation. Whereas stimulating cells were without effect, added BF maintained both proliferative and cytotoxic activity of the cells in culture. These observations, together with previous results, were interpreted to suggest that helper cells may regulate the activation of cytotoxic lymphocytes by means of soluble mediators.