In contrast, Baltz et al. reported that engagement of GITR on activated NK cells by soluble (s) GITRL (from cultures of tumor cells) or GITRL-Ig fusion protein or GITRL expressed on the tumor target cells inhibited NK cell functions (cytotoxicity and IFN-γ) (Baltz et al., 2007, 2008). The gene discussed is TNFRSF18; the disease is neoplasm.