Three FcgammaR family members, FcgammaRIIa, FcgammaRIIIa and FcgammaRIIIb, display functional bi-allelic polymorphisms (FcgammaRIIa: H131 vs. R131; FcgammaRIIIa: V158 vs. F158; FcgammaRIIIb: NA1 vs. NA2), and determine the efficacy of IgGmediated cellular inflammatory responses.