Interleukin-10 containing normal human serum inhibits granzyme B release but not perforin release from alloreactive and EBV-specific T cell clones

Abstract

Interleukin-10 (IL-10), also known as cytokine synthesis inhibitory factor, has pleiotropic effects in immunoregulation and inflammation. It is capable of inhibiting synthesis of pro-inflammatory cytokines like interferon [gamma] (IFN[gamma]), IL-2, IL-3, tumor necrosis factor [alpha] (TNF[alpha]) and granulocyte macrophage colony stimulating factor (GM-CSF) made by cells such as macrophages and T helper Type 1 cells. We observed that normal human serum, derived from a healthy individual but containing large amounts of IL-10 (arbitrarily designated as "IL-10 serum"), inhibited cytotoxic activity and interfered with granzyme B release from alloreactive cytotoxic T cell clones in vitro, but did not affect perforin release. The addition of normal human serum containing high levels of anti-IL-10 IgG (arbitrarily designated as "anti-IL-10 IgG serum") neutralized the inhibitory effects of IL-10 serum. Moreover, we have identified that cytotoxic activity and granzyme B release from an Epstein-Barr virus (EBV)-specific cytotoxic T cell clone was similarly inhibited in the presence of IL-10 serum, while perforin release was unaffected. Anti-IL-10 IgG serum also appeared to neutralize the inhibitory effect of IL-10 serum on an EBV-specific T cell clone. When anti-IL-10 IgG was depleted from anti-IL-10 IgG containing serum (arbitrarily designated as "anti-IL10 IgG free serum"), the neutralizing effect disappeared for both alloreactive and an EBV-specific T cell clone.