Effective in vitro clearance of Porphyromonas gingivalis by Fc alpha receptor I (CD89) on gingival crevicular neutrophils

Porphyromonas gingivalis has been implicated as a causative pathogen in per iodontitis. Immunotherapeutic approaches have recently been suggested to ai d in the clearance of P, gingivalis from disease sites. Because antibody-Fe receptor (FeR) interactions play a role in the effector functions of polym orphonuclear neutrophils (PMN), we evaluated which FeR on PMN from gingival crevicular fluid (GCF) serves as an optimal target molecule for FcR-direct ed immunotherapy. GCF PMN and peripheral blood (PB) PMN from adult periodon titis patients were analyzed for their immunoglobulin G (IgG) and IgA FcR ( Fc gammaR and Fc alphaR, respectively) expression and function by studying IgG- and IgA-mediated elimination of P. gingivalis. GCF PMN exhibited highe r Fc alpha RI and Fc gamma RI levels and lower Fc gamma RIIa and Fc gamma R IIIb levels than PB PMN. Functional studies revealed that GCF PMN exhibited less of a capacity to phagocytose and kill IgG1-opsonized P. gingivalis th an PB PMN. IgA1-mediated phagocytosis and killing capacity was, however, co mparable between GCF PMN and PB PMN. In summary, these in vitro results doc ument that Fc alpha RI represents a candidate target for FcR-directed immun otherapy for the clearance of P. gingivalis.