CXCR4^E343K is a gain-of-function mutation: analysis in primary leukocytes from patients with WHIM syndrome. (A-B) CXCR4 expression on PBMCs. Cells were gated on lymphocytes and monocytes. Representative zebra plots are shown in panel A and summary data in panel B. Percentages of CXCR4⁺ and CXCR4⁻ cells in PBMCs are shown. (C) PBMC calcium-flux responses to 10nM CXCL12. (D) Patient and HD PBMC calcium-flux responses to CXCL12 can both be blocked by plerixafor. CXCL12 was added after 3 minutes of incubation with the indicated concentrations of plerixafor. (E) Representative CXCR4 expression on neutrophils from an HD and from P1. Shaded area is unstained; solid line, CXCR4; dashed line, isotype control. (F) Neutrophil chemotaxis. Comparisons are displayed of a HD versus P1 and P2 for different concentrations of CXCL12-induced chemotaxis. Chemotactic index was defined as 1 when no CXCL12 was added to the lower chamber. Results from both patients were averaged and graphed, with SEM displayed for each value. *P < .05; **P < .01; and ***P < .001 for the comparison between HDs and CXCR4^E343K (E343K) patients, respectively.