Genetic variants of properdin factor B (Bf) in rheumatoid arthritis

Properdin factor B (Bf) phenotyping was carried out in 392 patients with rheumatoid arthritis (RA) and in 360 controls. In RA there were increased frequencies of both the Bf*S gene (83 vs 78%; pc = 0.0003) and the BfSS genotype 73 vs 61%; pc = 0.0002) and reduced frequencies of the Bf*F1 gene (0.5 vs 2.2%; pc = 0.03) and the BfFS genotype (20 vs 29%; pc = 0.0007). The frequencies of Bf*S in DR4 positive and DR4 negative RA were similar so that the findings were not accounted for by linkage disequilibrium between DR4 and Bf*S.