ANTI-CD3-ACTIVATED KILLER T-CELLS - INTERFERON-GAMMA AND INTERLEUKIN-10 CROSS-REGULATE GRANZYME-B EXPRESSION AND THE INDUCTION OF MAJOR HISTOCOMPATIBILITY COMPLEX-UNRESTRICTED CYTOTOXICITY

We have investigated the effect of interferon-gamma (IFN-gamma) and in terleukin (IL)-10 on granzyme B expression and the induction of major histocompatibility complex (MHC)-unrestricted cytotoxic activity in mo use T cell cultures following activation with anti-CD3 monoclonal anti body (mAb), First, metabolic inhibitors of granule-dependent and granu le-independent cytolytic pathways were used to show that anti-CD3-acti vated killer T (AK-T) cells kill allogeneic P815 mastocytoma target ce lls primarily by the granule-dependent granzyme/perforin pathway, In c omparison to control AK-T cells, lower levels of cytolytic activity we re evident when AK-T cells were generated in the presence of anti-IFN- gamma neutralizing mAb or exogenous IL-10, whereas enhanced cytotoxici ty was observed when AK-T cell cultures contained anti-IL-10 neutraliz ing mAb or exogenous IFN-gamma. In addition, granzyme B mRNA expressio n by AK-T cells was diminished when IFN-gamma bioactivity was neutrali zed or exogenous IL-10 was present in AK-T cell-cultures, whereas neut ralization of IL-10 bioactivity or the addition of exogenous IFN-gamma resulted in increased expression of granzyme B mRNA, Similar results were obtained when granzyme B enzymatic activity in AK-T cell lysates was quantified using a colorimetric granzyme B assay, Altered cytotoxi c potential, granzyme B mRNA expression, and granzyme B enzymatic acti vity following T cell activation in the presence of anti-IFN-gamma or anti-IL-10 neutralizing mAb or exogenous IFN-gamma or IL-10 could not be attributed to gross changes in T cell activation status or to alter ed percentages of CD4(+) and CD8(+) T cells in AK-T cell cultures, We conclude that IFN-gamma and IL-10 cross-regulate the induction of the granule-dependent cytolytic machinery of AK-T cells.