Objective: Fc gamma receptors of class IIa (Fc gamma RIIa) occur in 2 allelic forms, with either a low (IIa-R131) or a high (IIa-H131) affinity for complexed IgG2 and IgG3. This polymorphism might have implications for the handling of immune complexes. Therefore, we determined the distribution of the Fc gamma RIIa allotypes in patients with systemic lupus erythematosus (SLE), with or without a history of lupus nephritis.
Methods: We studied 95 unrelated white European patients with SLE, as defined by the American College of Rheumatology criteria, 50 of whom had a history of lupus nephritis, and 69 healthy white European control subjects. Fc gamma RIIa allotypes were determined by immunophenotyping of blood monocytes.
Results: It was found that lupus nephritis was significantly associated with the "low affinity" Fc gamma RIIa R/R131 allotype and with the R131 allele, compared with healthy controls. No significant association was found upon comparison of groups with and without nephritis.
Conclusion: SLE patients with a history of lupus nephritis have an abnormal distribution of Fc gamma RIIa allotypes. Fc gamma RIIa may well play a role in the pathogenesis of lupus nephritis, since IIa-R/R131 SLE patients seem to have a higher incidence of developing this complication.