Objective: To determine whether the simultaneous administration of drugs and/or cytokines such as transforming growth factor beta (TGFbeta) can render oral tolerance to type II collagen (CII) more effective in causing resistance to collagen-induced arthritis (CIA) in mice, and to investigate whether oral tolerance can still be induced when high levels of anti-CII are present.
Methods: Tolerance was induced by intragastric feeding of low-dose CII to DBA/1 mice during a 2-week period, either before immunization with CII in Freund's complete adjuvant or after initiation of arthritis. Some mice were simultaneously injected with TGFbeta1 or with the H2 receptor agonist dimaprit.
Results: Both TGFbeta1 and dimaprit increased the degree of oral tolerance obtained. TGFbeta1 augmented the induction of immunoregulatory CD8 T cells, which transferred the resistance to CIA induction to normal recipients. Feeding of CII for 2 weeks, starting after the onset of arthritis, still significantly ameliorated the course of CIA.
Conclusion: Administration of TGFbeta1 or dimaprit, both of which are believed to promote the development of immunoregulatory T cells, may reinforce induction of oral tolerance, even after the onset of arthritis.