The Salih group reported that, besides 4-1BBL, high expression of GITRL was observed on leukemia cells in many patients with AML (34/60; 57%) and CLL (47/60; 78%), but 4-1BB and GITR were absent on healthy CD34+ hematopoietic stem cells (Baessler et al., 2009; Buechele et al., 2012b). Here, TNFSF18 is linked to leukemia.