NEUTROPHIL-SPECIFIC ANTIGEN NB1 INHIBITS NEUTROPHIL-ENDOTHELIAL CELL-INTERACTIONS

Neutrophil-specific antigen NB1 is located on a 58 to 64 kd glycosyl p hosphatidylinositol-linked plasma membrane glycoprotein. NB1 antigen c an be detected on neutrophils from 97% of healthy volunteers, and NB1 antigen is expressed on subpopulations of neutrophils. Neutrophil subp opulations with varying functions have been described, and we hypothes ize that NB1 antigen may play an important role in neutrophil function . We compared the function of NB1-positive and NBI-negative neutrophil s obtained from several persons. There were no differences in the adhe sion of NBI-positive and NB1-negative neutrophils incubated in C5a, N- formyl-Met-Leu-Phe (FMLP), phorbol myristate acetate (PMA], or buffer to type IV collagen, fibronectin, laminin, or polystyrene. However, th e adherence to human umbilical vein endothelial cells (HUVEC) monolaye rs of unstimulated NB1-positive neutrophils was less than to NBI-negat ive neutrophils (20.0% +/- 4.2% vs 31.7% +/- 5.8%; p < 0.01). When neu trophils were stimulated with C5a, PMA, or FMLP, no differences were f ound in the adhesion of NBI-positive and NBI-negative cells to the sam e surfaces. When NBI-positive neutrophils were incubated with rabbit p olyclonal anti-NBI Fab fragments, their adherence to HUVEC was increas ed (32.9% +/- 10.1% vs 18.3% +/- 5.0%; p < 0.05). Fab fragments prepar ed from normal rabbit serum had no effect on neutrophil adherence to H UVEC. The chemotaxis of NBI-positive neutrophils to FMLP through nitro cellulose was significantly greater than that of NBI-negative neutroph ils (p = 0.03), but there was no difference in chemotaxis to FMLP thro ugh polycarbonate membranes. No differences were found between NBI-pos itive and NB1-negative neutrophils in chemotaxis to C5a, respiratory b urst response to PMA, or opsonized zymosan as measured by chemilumines cence. In summary, NBI antigen inhibits the adhesion of unstimulated n eutrophils to HUVEC and we speculate that NBI antigen may play a role in the margination of neutrophils.