Shin Yoshino, Raktham Maktrirat and Nobuaki Mizutani
Fabs fragments (Fabs) maintain binding ability to specific antigens, but lack the binding site for complements and for receptors on leukocytes that play a crucial role in Rheumatoid Arthritis (RA). In the present study, we investigated whether type II Collagen (CII)-Induced Arthritis (CIA) in mice was suppressed by anti-CII Fabs prepared by papain digestion of anti-CII antibodies. CIA was induced in DBA/1J mice by immunization with chicken CII and completes Freund’s adjuvant. To investigate the effect of anti-CII Fabs on the CIA model, mice were injected intraperitoneally with anti-CII Fabs 1 day before the first immunization. As a result, CIA was markedly inhibited by anti-CII Fabs; furthermore, the histological features of anti-CII Fabs-untreated mice included severe hyperplatic synnovium, cartilage and joint destruction, and leukocytic infiltration, whereas animals given anti-CII Fabs showed significant reduction of these histological changes. Additionally, antigen-specific suppression of CIA by anti-CII Fabs was related to the reduced levels of complement C3a in serum. Meanwhile, in vitro studies revealed that anti-CII Fabs significantly blocked the binding of intact anti-CII antibodies and also decreased complement activation. Collectively, the development of CIA was suppressed by anti-CII Fabs, which prevented the binding of anti-CII antibodies to antigen followed by the inhibition of complement activation, suggesting that autoimmune arthritic diseases such as RA may be specifically treated with pathogenic antibody Fabs.
