CD8A and neoplasm: In addition, recent studies have shown that Helicobacter pylori infection can inhibit the proliferation and antitumor effects of CD8+ T cells, promote the differentiation of naive T cells to Tregs, and regulate the expression of inflammatory factors; thus, affecting the tumor immune microenvironment, suppressing the host immune response, and reducing the efficacy of immunotherapy for gastric cancer (33–35).