As suggested by the analyses of the disorder XLP, which is characterized by SAP deficiency and a decrease in cytotoxic function of NK cells and EBV-specific CD8+ T cells, the apparent activating effect of CD244 in human NK cells and CD8+ T cells may relate to preferential expression of SAP [32], [56], [62]–[64]. The gene discussed is CD244; the disease is hyperinsulinemic hypoglycemia, familial, 4.