After detecting various related receptors on the surface of TILs, Kansy et al. found that the expression of PD-1 on the surface of CD8 + TILs (PD-1 + /CD8 + TILs) in HPV + OPSCC was significantly different from that in HPV − tumor tissues, while there was no significant difference in the expression of PD-1 on other types of TILs (such as CD3 + TILs, CD4 + TILs and CTLA-4 + TILs). Here, CD4 is linked to neoplasm.