In this study, we present an evaluation of the DC subset and CD4/CD8 + T cells in peripheral blood and cancer tissue samples as well as Foxp3 + Tregs and IDO expression in gastric cancer tissue, with the objective of determining whether peripheral and tumor‐infiltrating CD4/CD8 + T cells, DC subsets, and Tregs were correlated with each other and IDO expression as well as correlated with the clinicopathological features of gastric cancer and its prognosis. This evidence concerns the gene CD8A and cancer.