Interleukin 10 enhanced CD8+ T cell activity and reduced CD8 T cell apoptosis in patients with diffuse large B cell lymphoma.

The pleiotropic cytokine interleukin (IL)-10 is best characterized by its ability to downregulate inflammation and promote peripheral tolerance. On the other hand, IL-10 was also found to maintain the effector response of CD8 T cells and promote the expansion of tumor-resident CD8 T cells. In diffuse large B cell lymphoma (DLBCL), the role of IL-10 has been characterized in tumor cells but not in CD8 T cells. We found that CD8 T cells in DLBCL presented robust interferon (IFN)-γ expression early during TCR-activation but could not maintain this response later on, which was characterized by significantly lower CD8 T cell degranulation and higher apoptosis. These observations were associated with higher PD-1 expression in DLBCL CD8 T cells. Furthermore, the PD-1 cells were strongly enriched in the IFN-γ, but not the IFN-γ, fraction. Interestingly, exogenous IL-10 significantly improved the survival of DLBCL CD8 T cells, and resulted in significantly higher IFN-γ, ganzyme A and granzyme B expression in the absence of CD19 tumor cells, and significantly improved CD8 T cell-mediated specific lysis of CD19 tumor cells. IL-10 did not alter the expression of PD-1 in DLBCL CD8 T cells, but curiously, IL-10-treated DLBCL CD8 T cells were less susceptible to PD-L1-mediated apoptosis. We then demonstrated that IL-10 treatment significantly elevated the expression of pro-survival factor Bcl-2. Blocking IL-10 resulted in higher apoptosis, fewer IFN-γ CD8 T cells, and lower Bcl-2 expression. IL-10 also significantly increased STAT3, but not STAT1, phosphorylation in CD8 T cells. Together, these results suggested that IL-10 could enhance CD8 T cell inflammation in DLBCL patients.