CXCR5+CD8+ T cells present elevated capacity in mediating cytotoxicity toward autologous tumor cells through interleukin 10 in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is a common and aggressive subtype of non-Hodgkin's lymphomas, with limited treatment options in refractory and relapsed patients. Growing evidence supports the notion that CD8+ T cell immunity could be utilized to eliminate B cell lymphomas. CXCR5+CD8+ T cell is a novel cell subtype and share CXCR5 expression with CD19+ tumor cells. In this study, we investigated the frequency and function of existing CXCR5+CD8+ T cells in DLBCL patients. We found that DLBCL patients as a group demonstrated significantly higher level of CXCR5+CD8+ T cells than healthy individuals, with huge variability in each patient. Using anti-CD3/CD28-stimulated CD8+ T cells as effector (E) cells and autologous CD19+ tumor cells as target (T) cells, at high E:T ratio, no difference between the intensities of CXCR5+CD8+ T cell- and CXCR5-CD8+ T cell-mediated cytotoxicity were observed. However, at intermediate and low E:T ratios, the CXCR5+CD8+ T cells presented stronger cytotoxicity than CXCR5-CD8+ T cells. The expressions of granzyme A, granzyme B, and perforin were significantly higher in CXCR5+CD8+ T cells than in CXCR5-CD8+ T cells, with no significant difference in the level of degranulation. Tumor cells in DLBCL were known to secrete high level of interleukin 10 (IL-10). We therefore blocked the IL-10/IL-10R pathway, and found that the expressions of granzyme A, granzyme B, and perforin by CXCR5+CD8+ T cells were significantly elevated. Together, these results suggest that CXCR5+CD8+ T cells are potential candidates of CD8+ T cell-based immunotherapies, could mediate elimination of autologous tumor cells in DLBCL patients, but are also susceptible to IL-10-mediated suppression.