Neutrophil responses to CRP are not dependent on polymorphism of human FcγRIIA (R131H)

IgG2a mediated in vitro phagocytosis is less effective for individuals homozygous for Fcgamma RIIaR131 allele and such individuals are also more susceptible to certain infections. It has been reported that CRP binds to Fcgamma RIIaR131 but not Fcgamma RIIaH131 and since Fcgamma RIIa is also a major Fc receptor on neutrophils it would be expected that normal healthy donors who did not have at least one copy of Fcgamma RIIaR131 would not respond to CRP. We examined responses reported to be dependent on FcgammaRIIa but no difference between groups was observed in CRP mediated phagocytosis of S. pneumoniae, reactive oxygen production, or IL-8 synthesis. This suggests that either neutrophil receptors other than Fcgamma RIIa are responsible for CRP mediated responses or differences in CRP binding to the forms of Fcgamma RIIa are comparatively minor.