lgG2 antibody is the essential subclass to protect against encapsulated bacteria Fc$gamma$Rlla is the only Fc$gamma$ receptor that interacts with human lgG2. The two genetically determined allotypes of human Fc$gamma$Rlla, Fc$gamma$Rlla-R131 and Fc$gamma$Rlla-H131 alleles have functionally different reactivities with lgG2 in vitro, and H/H-131 cells have markedly higher binding affinity for human lgG2. Homozygous Fc$gamma$Rlllb-NA1/NA1 PMNLs show higher phagocytic capacity than Fc$gamma$Rlllb-NA2/NA2 PMNLs. To evaluate in vivo significance of Fc$gamma$Rlla and Fc$gamma$Rlllb allotypes, we analyzed Fc$gamma$R allotypes in children with bacterial meningitis due to Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis. Fc$gamma$RII and Fc$gamma$Rlllb polymorphisms were determined by using quantitative flow cytometry. Fc$gamma$Rlla were studied in 23 children with bacterial meningitis and 50 healthy Turkish controls, and Fc$gamma$lllb in 18 and 43 such individuals, respectively. The distribution of Fc$gamma$Rlla in the healthy Turkish control group was found to be significantly different from that in the Chinese and Japanese population (p