Gastric cancer patients display a distinctive population of IFNg+ IL10+ double positive CD8 T cells, which persists longer during prolonged activation

IL10 is generally regarded as a broad-spectrum regulatory cytokine. However, the role of IL10 in CD8 T cells remains controversial. In this study, we investigated the characteristics of endogenous IL10 by CD8 T cells in gastric cancer (GC) patients. Using intracellular staining, we found that in both GC patients and healthy controls, the majority of IL10-expressing CD8 T cells also presented concurrent IFNg expression. Interestingly, the frequency of IFNg(+) IL10(+) CD8 T cells was significantly higher in GC patients than in healthy controls, while the frequency of IFNg (+) IL10 (-) CD8 T cells was significantly lower in GC patients than in healthy controls. Compared to the IFNg(-) IL10(-) CD8 T cells, both IFNg(+) IL10(-) and IFNg(+) IL10(+) CD8 T cells presented significantly higher expression of activation/inhibitory markers. Interestingly, the IFNg(+) IL10(+) cells presented lower PD1 and TIM3 and higher KLRG1 than the IFNg(+) IL10(-) CD8 T cells. Remarkably, the IFNg(+) IL10(+) CD8 T cells, but not the IFNg (+) IL10(-) CD8 T cells, were highly enriched in the CD45RO(+) CXCR5(+) subset. Prolonged activation resulted in significant enrichment of IFNg(+)IL10(-) CD8 T cells over time. Interestingly, compared to the CD45RO(+) CXCR5(+) CD8 T cells, the CD45RO(+) CXCR5(+) CD8 T cells presented stronger proliferation capacity at later stages of stimulation, and higher viability throughout the stimulation process. Overall, our investigation demonstrated that GC patients were enriched with a distinctive population of IFNg(+) IL10(+) double positive CD8 T cells, which resembled T follicular cytotoxic cells and could persist longer during prolonged activation.