T cell subsets in the human testis and their potential role in testicular germ cell tumors

T cells represent the major component of tumor-infiltrating lymphocytes (TIL) in testicular germ cell tumors (TGCT). Whereas the roles of rarer subtypes, such as regulatory (Treg) and follicular helper T (Tfh) cells have not been investigated in TGCT, these have each been associated with tumor progression and prognosis in other tumor entities. This study particularly focused on these rare T cells in human TGCT and showed that both rare T cells are abundantly found in TGCT, providing the first evidence that rarer T cell subtypes and their signaling molecules are of functional importance in the TGCT immune environment.