Calcium transients in activated T cells from WHIM patients. Fura-2-loaded lymphocytes of WHIM patient P3 or healthy subject stimulated with CXCL12 at 100 ng/mL. The calcium concentration (y-axis) obtained following normalization of fluorescence ratio as described in “Patients, materials, and methods” is plotted against time (x-axis). (A) Homologous desensitization of lymphocytes to CXCL12 was investigated by analysis of calcium transients in response to CXCL12 at 100 ng/mL or 10 ng/mL in cells previously exposed to the same concentration of the chemoattractant. (B) Lymphocyte desensitization in response to PMA was analyzed in patients and healthy subjects by stimulation of cell suspension with PMA at 1 ng/mL or 3 ng/mL following addition of CXCL12, as indicated in the figure.