Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Novel Fc gamma Receptor 3B Gene (FCGR3B) Allele Variants and Polymorphism Distribution in Brazilian Systemic Lupus Erythematosus Patients and Blood Bank Donors.

Santos2,  Viviane C., Grecco2,  Marcelle, Pereira2,  Kaline M. C., Andrade2,  Luis E. C., Silva1,  Neusa P.

Universidade Federal de São Paulo, São Paulo, Brazil
Universidade Federal de São Paulo, Brazil

Background:

Immunecomplex (IC) deposition is a characteristic feature of systemic lupus erythematosus (SLE) and several pieces of evidence point towards an inefficient IC clearance in SLE. Fc gamma receptors (FcgR) are involved in the uptake and degradation of ICs by a variety of cells. FcgRIIa, FcgRIIb, FcgRIIIa and FcgRIIIb are polymorphic in humans and some alleles have been associated with SLE susceptibility. The FcgRIIIb gene (FCGR3B) presents three alleles, HNA-1a, HNA-1b and HNA-1c, characterized by specific nucleotides at six different positions in the 3rd exon.

Objectives:

to determine FCGR3B polymorphic distribution and describe novel allelic variants present in SLE patients and blood bank donors, in Sao Paulo, Brazil.

Patient and Methods:

peripheral blood was obtained from 260 consecutive SLE patients, attending the outpatient clinic of the Rheumatology Division at Universidade Federal de Sao Paulo, and from 246 ethnic-matched blood bank donors in Sao Paulo, Brazil. All individuals signed the informed consent approved by the Institutional Ethics Board. DNA was extracted by salting out and a 243bp sequence containing the polymorphic region of interest of the 3rd exon of FCGR3B was amplified by PCR. All samples were sequenced and processed in capillary gel electrophoresis (ABI 3130xl).

Results:

Among SLE patients we found 52 homozygous for HNA-1a, and 208 heterozygous (188 HNA-1a/HNA-1b and 20 HNA-1a/HNA-1c). Among blood donors, HNA-1a homozygosis was found in 56, and heterozygosis in 190 (170 HNA-1a/HNA-1b and 20 HNA-1a/HNA-1c). Novel allelic variants (one HNA-1a and three HNA-1b) were also found. Point mutations, previously described in nucleotides not related to allelic discrimination (G230T, A249G, and G330T) were observed in both SLE (57) and blood bank donors (60). In addition we also identified 22 new point mutations in 76 SLE patients and 66 blood bank donors. There was no statistical difference between groups regarding genotype or phenotype distribution. Interestingly, homozygous individuals for the HNA-1b allele were not found in the population under study.

Conclusion:

There was no association of FCGR3B gene polymorphism and SLE. Our results indicate that FCGR3B is a highly polymorphic gene possibly due to the existence of either somatic recombination or hyper mutation within this gene segment.

To cite this abstract, please use the following information:
Santos, Viviane C., Grecco, Marcelle, Pereira, Kaline M. C., Andrade, Luis E. C., Silva, Neusa P.; Novel Fc gamma Receptor 3B Gene (FCGR3B) Allele Variants and Polymorphism Distribution in Brazilian Systemic Lupus Erythematosus Patients and Blood Bank Donors. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :504
DOI: 10.1002/art.28273

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