Genetic variation of mannose-binding protein associated with glomerular immune deposition in IgA nephropathy

To investigate the relationship between codon 54 gene polymorphism of the host defense molecule, mannose-binding protein (MBP), and the patterns of glomerular immune deposition in IgA nephropathy (IgAN).

IgAN patients with different patterns of glomerular immune deposition were selected and divided into two groups. Group A consisted of 77 patients with glomerular IgA and C3 deposits, and Group AGM consisted of 70 patients with glomerular IgA, IgG, IgM, C3 and Clq deposits. Clinical features and laboratory relevant data of all patients were collected. One-hundred and forty healthy adults were recruited as normal controls. The MBP gene codon 54 GGC/GAC polymorphism was investigated by using polymerase chain reaction and restriction fragment length polymorphism.

The genotype frequency of GGC/GAC heterozygotes was significantly higher in Group AGM as compared with that of Group A (41.4% vs 19.5%, P < 0.01) or normal subjects (41.4% vs. 26.4%, P < 0.05), while no difference was found in the distribution of MBP genotypes between Group A and normal subjects. GAC allele frequency was also higher in Group AGM than that in Group A (0.24 vs. 0.14, P < 0.05) or normal subjects (0.24 vs. 0.15, P < 0.05). The variant allele (GAC) was markedly associated with Group AGM (OR = 1.95, 95% CI: 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 the onset of IgAN than those with wild homozygotes (GGC/GGC).

Genetic variation of the host defense molecule, MBP, may be involved in the formation of the diverse patterns of glomerular immune deposition in IgAN. The variant allele of the MBP gene may partially account for abundant immune deposits in some IgAN patients.