CD4 and neoplasm: It has been shown that radiotherapy, especially stereotactic split-course radiotherapy, releases a large number of tumor antigens from the irradiated lesion, which promotes antigen presentation by DCs cells, activates CD8+ T cells, CD4+ T cells, and NK cells stimulates the immune response, and regulates the changes in the tumor and its microenvironment, resulting in an “in situ vaccine” effect [14].