IMPAIRED MIGRATION IN-VITRO OF NEUTROPHILS FROM PATIENTS WITH PAROXYSMAL-NOCTURNAL HEMOGLOBINURIA

Migration of neutrophils in patients with paroxysmal nocturnal haemogl obinuria (PNH) was studied using two different complement-free in vitr o model systems, subagarose and transendothelial migration. In the sub agarose migration assay the mean migration distance of PNH neutrophils was slightly, but significantly, reduced to 1236 mu m (range 753-1586 , n = 6) compared to a normal mean of 1476 mu m (range 1076-1768, n = 6, P = 0.016). By immunocytochemical staining for the urokinase type p lasminogen activator receptor (uPAR) which is a glycosyl-phosphatidyl- inositol (GPI) anchored protein expressed by normal, but not by PNH-af fected, neutrophils, it was shown that the uPAR-positive subpopulation of normal neutrophils predominated among the faster migrating cells ( 60-80% normal cells at the front of migration) while uPAR-negative (i. e. PNH-affected neutrophils) were more numerous close to the applicati on well (5-30% normal cells). When migration of neutrophils was tested across a monolayer of human umbilical vein endothelial cells (HUVEC) cultured on polycarbonate filters, there was a 3-4-fold impairment of the migration of the PNH-affected neutrophils both in the absence of s timulation and after stimulation with fMLP (P<0.001 in both cases). Af ter IL-1 stimulation of the endothelium the impairment was even more p ronounced (8-fold difference, P<0.001). When the endothelial cells wer e grown on collagen-coated filters the impairment of the migration of PNH neutrophils was less pronounced, but still significant after stimu lation with fMLP and IL-1 (2-fold, P < 0.05 in both cases). These resu lts demonstrate that there is a complement-independent impairment of m igration of neutrophils from patients with PNH which may be related to their failure to express GPI-linked proteins involved in cell migrati on and/or adhesion such as the uPA receptor and the CD66b antigen.