Association of gene polymorphism of polymeric immunoglobulin receptor and IgA nephropathy

In order to explore the possibility that genetic predisposition to dysfunction of mucosal immunity and the IgA processing pathway plays a role in the pathogenesis of mesangial IgA1 deposition in IgAN, we examined the possible association of the gene polymorphism of pIgR in the patients with and without IgAN.

Genomic DNA of peripheral blood cells was isolated from 372 individuals including 172 histologically confirmed IgAN patients. Segments of the pIgR gene were PCR amplified and restriction fragment length polymorphism was determined as A1 and A2 with and without Pvu II site, respectively.

The pIgR genotype distribution was significantly different between the patients with IgAN and those without IgAN. Allele frequency of A2 was higher in IgAN than in other renal diseases (A1 and A2; 0.516 and 0.484 in IgAN, 0.641 and 0.359 in others, chi2 = 9.84, P = 0.0017, Odds ratio = 1.71). Moreover, the subjects with A2A2 genotype were associated with a relatively low level of serum IgA only in the patients with IgAN but not in other renal diseases. The difference of allele frequencies was more remarkable in the patients with a serum IgA level of less than 300 mg/dl (A1 and A2; 0.439 and 0.561 in IgAN, 0.702 and 0.298 in others, chi2 = 12.44, P = 0.0004, Odds ratio = 3.01).

This is the first demonstration of the pIgR gene polymorphisms in IgAN which are associated with its clinical phenotype. Gene polymorphisms of pIgR may be candidate genetic markers of susceptibility to IgAN.