Although expression of GITR, GITRL, 4-1BB, and 4-1BBL was comparable on NK cells of CLL patients and healthy individuals, T cells of healthy volunteers expressed higher levels of GITR, GITRL, 4-1BB, and 4-1BBL compared to CLL patients’ T cells. Here, TNFRSF18 is linked to B-cell chronic lymphocytic leukemia.