Absence of association between the Fc gamma receptor IIIA-176F/V polymorphism and the severity of malaria in Thai.

Human Fc gamma receptor (Fc gamma R) genes form a clustered gene family, which consists of Fc gamma RIIA, IIB, IIC, IIIA, and IIIB genes, on chromosome 1q23. We previously reported that the Fc gamma RIIA-131H/H genotype in combination with the Fc gamma RIIIB-NA2 allele is associated with susceptibility to cerebral malaria, and that such an association can be caused by linkage disequilibrium (LD) between these polymorphisms and the primary associated gene(s) in this region. Fc gamma RIIIA is known to exhibit the genetic polymorphism Fc gamma RIIIA-176F/V coded for different affinity to IgG1 and IgG3. In this study, we examined a possible association between Fc gamma RIIIA-176F/V polymorphism and severity of malaria in 462 adult Thai patients with Plasmodium falciparum malaria. The frequencies of Fc gamma RIIIA-176V among patients with mild malaria, with non-cerebral severe malaria, and with cerebral malaria were 32.7%, 29.9%, and 36.3%, respectively. This polymorphism showed neither positive nor negative association with the severity of malaria. Thus, we concluded that the association of Fc gamma RIIA-131H/R and Fc gamma RIIIB-NA1/NA2 polymorphisms with cerebral malaria in Thailand is not due to the LD caused by Fc gamma RIIIA-176F/V.