SH2D1A and X-linked lymphoproliferative syndrome: Given the broader role SAP plays in boosting TCR restimulation and enhancing the upregulation of multiple pro-apoptotic molecules, we now comprehend the fatal flaw of true RICD resistance in XLP-1 patients, in contrast to genetic defects in a single, downstream apoptotic pathway (e.g., Fas-induced defects in ALPS).