SH2D1A and X-linked lymphoproliferative syndrome: Notably, X-linked lymphoproliferative disease (XLP-1) patients with null mutations in the small signaling adaptor SLAM-associated protein (SAP) experience life-threatening accumulation of RICD-resistant T cells during certain viral infections (Sharifi et al., 2004; Bassiri et al., 2008; Snow et al., 2009).