Abstract： Objective To investigate the relationship between codon 54 gene polymorphism of the host d efense molecule, mannose-binding protein (MBP), and the patterns of glomerular immune deposition in IgA nephropathy (IgAN). Methods IgAN patients with different patterns of glomerular immune deposition were selec ted and divided into two groups. Group A consisted of 77 patients with glomerul ar IgA and C3 deposits, and Group AGM consisted of 70 patients with glomerular I gA, IgG, IgM, C3 and Clq deposits. Clinical features and laboratory relevant da ta of all patients were collected. One-hundred and forty healthy adults were r ecruited as normal controls. The MBP gene codon 54 GGC/GAC polymorphism was inv estigated by using polymerase chain reaction and restriction fragment length pol ymorphism.Results The genotype frequency of GGC/GAC heterozygotes was significantly higher in Grou p 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 f requency 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 episo des of upper respiratory or gastrointestinal infections prior to the onset of Ig AN than those with wild homozygotes (GGC/GGC).Conclusions Genetic variation of the host defense molecule, MBP, may be involved in the form ation of the diverse patterns of glomerular immune deposition in IgAN. The vari ant allele of the MBP gene may partially account for abundant immune deposits in some IgAN patients.