Chemotactic response to fMLP of neutrophils from patients with PNH. (A) PMNs isolated from the peripheral blood of 12 patients were evaluated for the expression of CD157 using RF3-FITC mAb. Cytofluorimetric analysis was performed on at least 10 000 cells. The results are expressed as percentage of CD157⁺ PMNs. (B) Summary of the results of migration of neutrophil from 12 patients with PNH (•)in response to 10 nM fMLP analyzed in parallel with 13 healthy donors (○). The increasing rate of fMLP-induced chemotaxis was evaluated as fMLP-induced migration/basal migration. P = .001. (C) Inhibitory effect of anti-CD157 mAb on neutrophil chemotaxis. The results are the average of 13 healthy donors analyzed and of 3 patients with PNH with a virtually absent (05, 09, 10), low (< 15%) (02, 06, 11), or significant (> 20%) (03, 04, 07) percentage of PMNs expressing CD157. Results are expressed as percentage of inhibition of fMLP-induced chemotaxis following CD157 ligation. (D) PMNs from the PNH07 patient with -30% normal neutrophils were enriched in GPI^- PMNs, by negative selection with anti-CD157–coated magnetic beads. (E) The impaired migration of neutrophils from the PNH07 patient (▪) is increased in the CD157-deprived population (▦). There were 5 fields counted per well, and neutrophil chemotactic response was expressed as the mean number of migrated cells per high power field from triplicate wells ± SD. ^*P < .05.