Evidence for auto-reactivity against the collectins, SP-A and MBL, in rheumatoid arthritis synovial fluids: Lack of cross-reactivity with C1q or type II collagen

Humoral autoreactivity directed against surfactant protein-A (SP-A) in rheumatoid arthritis synovial fluids.

SUMMARY SP-A is found principally in the lung, and has been associated with lamellar bodies also found in the synovial joint. Both SP-A and C1q contain collagen-like regions, and SP-A and C1q have some structural similarities, both having a globular head region and a collagen-like tail. Here we are able to show that (i) autoreactivity to SP-A, as expressed by IgG and IgM autoantibodies, is present in synovial fluid (SF) isolated from patients with rheumatoid arthritis (RA); (ii) in absorption experiments only a limited degree of cross-reactivity between autoantibodies reactive with C1q and SP-A is observed; (iii) there is no cross-reactivity between autoantibodies reactive with type II coll…