Functional consequences of the IL2RG mutation. (A) Expression of CD132 on B cells of the patient (gray line) and a healthy control (bold line; light line indicates isotype control). (B) STAT-5 phosphorylation after IL-2 stimulation in EBV-transformed B cells from a healthy donor (top panel), P2 (middle panel), and an X-SCID patient with a c.545G>A (Cys182Tyr) mutation. The gray lines represent isotype controls. (C) STAT-6 phosphorylation after IL-4 stimulation in EBV-transformed B cells. (D) STAT-6 phosphorylation after IL-4 stimulation of fresh B cells from a healthy donor (top) and P2 (bottom). (E) X-inactivation analysis of DNA obtained from sorted maternal T cells or T cell–depleted PBMCs. The CGG repeat within the FMR1 gene was amplified from undigested DNA (first and third panels) and after digestion with the methylation-sensitive restriction enzyme HpaII (second and fourth panels). Note the absence of a second PCR product in the second panel indicating completely skewed X inactivation.