Anti-CD3-activated killer T cells: Interferon-γ and interleukin-10 cross-regulate granzyme B expression and the induction of major histocompatibility complex-unrestricted cytotoxicity

We have investigated the effect of interferon-γ (IFN-γ) and interleukin (IL)-10 on granzyme B expression and the induction of major histocompatibility complex (MHC)-unrestricted cytotoxic activity in mouse T cell cultures following activation with anti-CD3 monoclonal antibody (mAb). First, metabolic inhibitors of granule-dependent and granule-independent cytolytic pathways were used to show that anti-CD3-activated killer T (AK-T) cells kill allogeneic P815 mastocytoma target cells primarily by the granule- dependent granzyme/perforin pathway. In comparison to control AK-T cells, lower levels of cytolytic activity were evident when AK-T cells were generated in the presence of anti-IFN-γ neutralizing mAb or exogenous IL- 10, whereas enhanced cytotoxicity was observed when AK-T cell cultures contained anti-IL-10 neutralizing mAb or exogenous IFN-γ. In addition, granzyme B mRNA expression by AK-T cells was diminished when IFN-γ bioactivity was neutralized or exogenous IL-10 was present in AK-T cell- cultures, whereas neutralization of IL-10 bioactivity or the addition of exogenous IFN-γ 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 cytotoxic potential, granzyme B mRNA expression, and granzyme B enzymatic activity following T cell activation in the presence of anti-IFN-γ or anti-IL-10 neutralizing mAb or exogenous IFN-γ or IL-10 could not be attributed to gross changes in T cell activation status or to altered percentages of CD4⁺ and CD8⁺ T cells in AK-T cell cultures. We conclude that IFN-γ and IL-10 cross-regulate the induction of the granule-dependent cytolytic machinery of AK-T cells.