Monoclonal anti-Ia antibodies suppress the flare up reaction of antigen induced arthritis in mice.

Intravenous injection of methylated bovine serum albumin (mBSA) in mice with a unilateral antigen-induced arthritis induced with mBSA causes a flare up of the inflammation in the arthritic but not in the contralateral joint. To study whether this phenomenon is dependent on class II antigens, we treated C57Bl/10 (H-2b) and C3H (H-2k) mice with monoclonal anti-Iab (HB26) and anti-Iak (2-2-1) antibodies on days -3, -2, -1 and 0 before induction of the flare up. Another group was treated only once on day 0 before antigen challenge. Four injections with HB26 completely suppressed the flare up reaction in C57Bl/10 mice; the same results were seen with 2-2-1 in C3H mice. One injection only partly suppressed the flare up reaction in both strains, whereas four injections with the haplotype-nonspecific antibodies did not affect the flare up. Injections with HB26 appeared to be able to completely suppress a delayed type hypersensitivity reaction but not a reversed passive Arthus reaction in C57B1/10 mice, indicating that anti-Ia antibodies have an effect on lymphocyte-dependent but not on antigen-antibody-dependent inflammatory phenomena. These results demonstrate that the flare up of antigen induced arthritis is dependent on the presence of Ia antigens, suggesting that the interaction between antigen-presenting cells and T lymphocytes plays an important role in this process.