Histograms demonstrating intracellular SH2D1A expression in patients with XLP. Flow cytometric analysis of intracellular SH2D1A expression. (A) Representative healthy control. (B) Normal expression, the father of patient 5 (P5). (C) XLP carrier, the mother of patient 1. P1 to P4 (D-G) are patients with confirmed mutations of the SH2D1A gene. Lymphocytes are gated and stained with anti-SH2D1A antibody (continuous lines) or irrelevant rat IgG (dashed lines) and additional FITC-labeled, antirat IgG antibody. *SH2D1A expression in CD56⁺ T cells of patient 3 was not measured (N/A) because the number of CD56⁺ T cells in his sample was too low.