CD8A and gastric cancer: However, tumor cells, in order to escape the immunocidal effect of the body, also produce immunosuppressive factors to inhibit the differentiation and proliferation of immune cells, researchers have detected decreased levels of immune cells and CD4+/CD8+ ratio in patients with lung, esophageal, colorectal, and gastric cancers (Chraa et al. 2019; Wang et al. 2021).