Mannose-binding lectin gene polymorphism associated with the patterns of glomerular immune deposition in IgA nephropathy

Objective: To elucidate the genetic background underlying the diversity of mesangial immune deposition in IgA nephropathy (IgAN), we investigated the distribution of mannose-binding lectin (MBL) gene codon 54 polymorphism and serum MBL levels in IgAN patients. Methods: Seventy-seven IgAN patients with glomerular IgA and C3 deposits (Group A) and 70 with glomerular IgA, IgG, IgM, C3 and C1q deposits (Group AGM) were included in the present study. Control group consisted of 140 normal adults. MBL genotypes were investigated by polymerase chain reaction and restriction fragment length polymorphism. Serum MBL levels with different genotypes were also assayed in some subjects. Results: The variant allele (GAC) was markedly associated with Group AGM (OR = 1.95, 95% C.I.: 1.06-3.58). In both Group A and Group AGM, more patients carrying the variant allele had episodes of upper respiratory or gastrointestinal infections prior to onset or exacerbation of IgAN than wild homozygotes (GGC/GGC). In addition, a significant difference in serum MBL level was also observed between wild homozygotes and heterozygotes (GGC/GAC) (GGC/GGC > GGC/GAC) (p < 0.0001) in all groups, while there was no difference for subjects with the same genotypes among the three groups (p < 0.05). Serum MBL levels of the rare variant homozygotes approached zero. Conclusions: Our findings provide evidence that the host defense molecule, MEL, may be involved in the formation of the diversity of glomerular immune deposition in IgAN. Genetic deficiency of MBL may partially account for abundant immune deposits in some IgAN patients.