TNFRSF18 and B-cell chronic lymphocytic leukemia: Figure 4A shows exemplary histogram plots for each surface marker of high and low expressing cells of patients. In order to further explore the impact of GITR/GITRL and 4-1BB/4-1BBL expression on survival in CLL and to evaluate the prognostic value of our selected cut-off, Kaplan-Meier analyses were performed. When grouped according to GITR expression, GITRhi cases had a tendency to longer OS (Figure 4B, p = 0.080). Median OS in GITRhi and GITRlo cases was not reached. In contrast, expression levels of GITRL did not at all correlate with OS (p = 0.987) (Figure 4C).