Association of C2 and CFB polymorphisms with anterior uveitis

Association of rs800292 (I62V) in the complement factor H (CFH) gene with anterior uveitis (AU) was identified in our previous study. We proceeded to investigate whether polymorphisms of two tightly linked genes in the complement pathway, complement component 2 (C2) and complement factor B (CFB), are associated with AU.

Five single-nucleotide polymorphisms (SNPs), rs1048709, rs537160, rs4151657, rs2072633 in CFB, and rs3020644 in C2, were examined using genotyping assays in 98 Chinese AU patients and 291 unrelated controls. Adjustments and stratifications were given for sex, clinical manifestations, and HLA-B27 status.

There were significant increases in the frequency of A allele and AA homozygosity for CFB-rs1048709 in AU patients compared with that of controls (P value after Bonferroni correction [P(corr)] = 2.67 × 10⁻⁴, P(corr) = 0.001, respectively). No association was found between AU and the other four SNPs after adjustment for multiple testing. Logistic regression analysis showed none of the 5 SNPs had significant interaction with sex. Stratified analyses showed that only rs1048709 was significantly associated with AU in HLA-B27-positive patients but not in HLA-B27-negative patients. No association was found in the 5 tested SNPs with clinical manifestations. A haplotype block across CFB (AATA) was significantly predisposed to AU with increased risk of 1.97 (P(corr) = 0.0005). Additive effect of CFB-rs1048709 and CFH-rs800292 was identified with an odds ratio of 7.48.

Our results revealed an association between AU and CFB-rs1048709. The influence on AU might differ depending on HLA-B27 status. The joint effect in CFB and CFH strengthens the concept that the complement system plays an important role in the pathogenesis of AU.