IMMOBILIZED IGG AND FIBRINOGEN DIFFERENTIALLY AFFECT THE CYTOSKELETALORGANIZATION AND BACTERICIDAL FUNCTION OF ADHERENT NEUTROPHILS

The infection of a vascular prosthesis is a dreaded clinical outcome. Since fibrinogen (FBGN) and immunoglobulin (IgG) coat the implanted bi omaterial surface, it is with these immobilized proteins that the neut rophil (PMN) interacts. This study tests the hypothesis that PMN are i mpaired in their ability to kill bacteria when bound to immobilized Ig G or FBGN. Isolated human PMN were bound to FBGN or IgG: and then left untreated or exposed to phorbol myristate acetate (PMA; 10(-7) M). PM N adhered loosely, but did not spread, onto FBGN. In contrast, PMN spr ead fully onto IgG, exhibiting polarized pseudopodia. PMA treatment in duced spreading of the FBGN bound cells. Suspended and adherent PMN we re incubated 1 h with C-14-labeled Staphylococcus aureus; then, phagoc ytosis was assessed by radioactive uptake or bacterial kill. was deter mined by plating recovered bacteria and colony counting. Data were ana lyzed by unpaired t test. We observed that both the phagocytic and the killing ability of FBGN-bound PMN were similar to that of suspended P MN. Conversely, IgG-bound PMN displayed a 62 +/- 6% (P < 0.01) decreas e in phagocytosis and 33 +/- 7% (P < 0.05) reduction in bill vs suspen ded cells. PMA induced a 74 +/- 6% (P < 0.01) reduction in phagocytosi s and 68 +/- 5% (P < 0.01) reduction in kill of bacteria for PMN bound to FBGN with no further effect on IgG-bound PMN. Using fluorescent vi tal dyes and confocal microscopy we determined that 33% fewer PMN were engaged in phagocytosis when bound to IgG vs FBGN. We conclude that F c receptor ligation by immobilized IgG or PMA treatment of the FBGN-ad herent PMN triggers cell spreading and reduced bactericidal activity. These results indicate that excessive cytoskeletal organization may im pair the ability of PMN to kill bacteria and result in vascular graft infections. (C) 1998 Academic Press.