TNFRSF18 and B-cell chronic lymphocytic leukemia: NK cells of CLL patients were shown to have GITR, GITRL, 4-1BB, and 4-1BBL expression levels up to SFIs of 25.2, 3.7, 7.1, and 6.9, whereas T cells of the same patients expressed SFIs up to 3.1, 1.7, 1.8, and 1.5, respectively (Figure 2A–D).