FCGR3B*03 allele inheritance pattern in Brazilian families and some new variants of gene FCGR3B.

BACKGROUND

The FCGR3B gene encoding the FcyRIIIb receptor for immunoglobulin G has three polymorphic forms known as HNA-1a, HNA-1b, and HNA-1c, encoded by the alleles FCGR3B01, FCGR3B02, and FCGR3B03, respectively. It is not clear whether the inheritance of the FCGR3B03 allele, which encodes the HNA-1c, is linked or not to the other two alleles. The objective of this study was to identify the inheritance pattern of the FCGR3B*03 allele in Brazilians.

STUDY DESIGN AND METHODS

Blood samples from nine families with at least one FCGR3B03(+) member, totalizing 47 individuals, were studied. The presence of the FCGR3B01, FCGR3B02, and FCGR3B03 alleles was detected by the polymerase chain reaction with sequence-specific priming method, and all DNA samples were sequenced.

RESULTS

In three of the nine studied families, the FCGR3B03 was passed down with the FCGR3B02, while in one family the FCGR3B03 was inherited in linkage with FCGR3B01. The other families were not informative regarding FCGR3B03 inheritance. Sequencing showed for the first time one single-nucleotide polymorphism at Position 264 resulting from a simple substitution C→T; three other different substitutions at Position 230, T→A, T→G; and the presence of three nucleotides at Position 230 (T, G, and A). The previously reported variants FCGR3B01A227G and FCGR3BG330T were also found.

CONCLUSION

In this Brazilian FCGR3B03(+) group we found that the inheritance of FCGR3B03 took place by a linkage to FCGR3B02 or to FCGR3B01. Linkage of FCGR3B03 to FCGR3B02 was the most common. Additionally, we report SNPs that have not been described, suggesting that they might be more common than previously thought.