Interleukin 10 promotes immune response by increasing the survival of activated CD8⁺ T cells in human papillomavirus 16-infected cervical cancer

Human papillomavirus (HPV)-specific CD8⁺ T cells are present in HPV-infected cervical cancer patients and have demonstrated potent antitumor properties. However, these cells cannot control tumor progression in most patients. To investigate the underlying mechanisms involved in suppressing or promoting CD8⁺ T cell functions, we focused on interleukin 10 (IL-10), a pleiotropic cytokine with controversial roles in antitumor immunity. We found that compared to healthy controls, circulating CD8⁺ T cells in HPV 16-infected cervical cancer patients expressed significantly higher levels of IL-10. Interestingly, these CD8⁺ T cells from cervical cancer patients, but not those from healthy controls, responded to HPV 16 E6/E7 peptide stimulation by increasing IL-10 expression, demonstrating an antigen-specific IL-10 release. Addition of exogenous IL-10 improved the survival, but did not increase the proliferation, of peptide-stimulated CD8⁺ T cells. CD8⁺ T cells cultured in the presence of IL-10 also resulted in significantly higher interferon gamma (IFN-gamma) and granzyme B concentration, primarily due to improved cell survival. In resected cervical tumors, the frequency of tumor-infiltrating IL-10⁺ CD8⁺ T cells was positively correlated with the frequency of tumor-infiltrating IFN-gamma⁺ and granzyme B⁺ CD8⁺ T cells. Tumor-associated macrophages were more potent than peripheral blood monocyte-derived macrophages at inducing IL-10 expression in CD8⁺ T cells, possibly explaining the elevated IL-10⁺ CD8⁺ T cell frequency in cervical cancer patients. Together, these results are consistent with an immunostimulatory role of IL-10, which promoted CD8⁺ T cell response by increasing the survival of activated CD8⁺ T cells.