By using gastric cancer-derived exosomes with different differentiation status (well differentiated gastric cancer cell line MKN-28, poorly differentiated gastric cancer cell line MKN-45, and moderately differentiated gastric cancer cell line SGC-7901), we investigated the effect of gastric cancer exosomes on CD8+ T cells by specifically focusing on cell cycle progression, apoptosis, cytokine secretion, and gene expression. The gene discussed is CD8A; the disease is gastric cancer.