Analysis of the CXCR4 ORF in patients with WHIM. (A) Patients P1 and P2 (pedigree I) inherited the disease-associated haplotype from their father. Patient P3 (pedigree II) inherited the disease-associated haplotype from her father. Patient P4 (pedigree III) is the fourth child of healthy, nonconsanguineous parents and might constitute a sporadic case. (B) Electrophoregram of the CXCR4 cDNA sequence from patient P1 (right panel) encompassing a C1013 → G substitution. The same mutation was detected in patient P2. Left panel shows for patient P3 the equivalent CXCR4 cDNA wild-type sequence. (C) In the amino acid sequence of the CXCR4 C-tail, the mutation recovered in patients P1 and P2 introduces a nonsense codon (underlined) in place of Ser-338. The previously reported WHIM-associated CXCR4¹⁰⁰⁰ is shown.²⁴  (D) Cell surface expression of CXCR4 in CD3⁺-gated PBMCs from the 4 patients and 2 independent healthy donors was determined by flow cytometry using the PE-conjugated 12G5 (empty histograms) or isotype control (gray histograms) monoclonal antibody (mAb).