Bf and C3 polymorphisms in rheumatoid arthritis.

Properdin factor B (Bf) and complement C3 polymorphisms were studied in 225 unrelated rheumatoid arthritis (RA) patients from North-East England. Patients were subdivided on the presence or absence of significant titres of rheumatoid factor and antinuclear factor. No association with the C3 system was detected. For the Bf system, a significant excess of Bf SS and deficiency of Bf FS phenotypes was observed in seropositive RA patients lacking antinuclear antibodies. This finding suggests that auto-antibody-defined subgroups of RA may be genetically heterogeneous with respect to Bf and confirms the status of Bf SS phenotype as a marker for RA susceptibility and/or severity.