HTR2B is closely related to the regulation of tumor microenvironment.[46] Related studies have found that HTR2B positively correlates with the infiltration of CD8+ T cells, macrophages, and other immune cells in the tumor microenvironment during the progression of breast cancer and gastric cancer.[47] Our study investigates the impact of HTR2B on the tumor microenvironment, and found that activation of HTR2B can promote OASL1+ macrophage production to enhance antitumor immunity through multiple pathways. The gene discussed is CD8A; the disease is gastric cancer.