[Study of polymorphism of Fc gamma IIa receptors in Chilean patients with systemic lupus erythematosus].
BACKGROUND
Polymorphisms of Fc receptors for IgG (Fc gamma R) have been proposed as a genetic factor that influences susceptibility for systemic lupus erythematosus (SLE). Human Fc gamma RIIa has 2 codominantly expressed alleles, H131 and R131, which differ at amino acid position 131 in the second extracellular domain (histidine or arginine respectively) and differ substantially in their ability to bind human IgG2. The H131 allele binds IgG2 efficiently, whereas R131 binds it poorly. Because IgG2 is a poor activator of the classical complement pathway, the H131 is essential for the disposal of IgG2 immune complexes.


OBJECTIVE
To determine the distribution of Fc gamma RIIA genes in a cohort of Chilean SLE patients, with or without a history of lupus nephritis.


METHODS
We studied 52 Chilean SLE patients fulfilling the 1982 American College of Rheumatology (ACR) criteria, 20 of whom had a history of nephritis, and 44 ethnically matched disease-free controls. Fc gamma RIIa allotypes were genotyped by PCR.


RESULTS
No significant association was observed between the low affinity Fc gamma RII receptor (FcgRIIa-R131) and the presence of SLE or lupus nephritis. However, genotype frequencies in SLE patients but not in controls, departed from the proportions predicted by the Hardy-Weinberg equilibrium, suggesting this locus might be related to the disease.


CONCLUSIONS
Our results suggest that in Chilean patients with SLE, as well as in many other populations, the R131 allotype is not a major factor predisposing to the development of SLE or lupus nephritis.
Carrión
Flavio
F
Facultad de Medicina, Universidad de los Andes, Facultad de Medicina, Pontificia Universidad Católica de Chile, Facultad de Medicina, Sede Oriente, Universidad de Chile.
Figueroa
Fernando
F
Martínez
M Eugenia
ME
Massardo
Loreto
L
Pérez
Tamara
T
Foster
Carolina
C
Mancilla
Cecilia
C
Neira
Oscar
O
Guzmán
Leonardo
L
Valenzuela
Viviana
V
Urrutia
Ramón
R
Carmona
Sergio
S
Figueroa
Maximiliano
M
Lubiano
Alessandra
A
Wainstein
Eduardo
E
D000483:Alleles; D015703:Antigens, CD / Q000235:genetics*; D002677:Chile; D015331:Cohort Studies; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000235:genetics*; D008181:Lupus Nephritis / Q000235:genetics; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D017452:Receptors, IgG / Q000235:genetics*
D015703:Antigens, CD; C080568:Fc gamma receptor IIA; D017452:Receptors, IgG