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

Abstract

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 granuledependent 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 AKT 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 IFNγ. 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.