Production of a macrophage migration inhibitory factor in rabbits with experimental arthritis.

Cultures of synovial tissue from rabbits with an antigen-induced arthritis were tested for production of macrophage migration inhibitory factor to investigate the possible role of cellular immunity in this experimental model. Culture supernatants of ten specimens of normal rabbit synovium and six specimens from joints injected with saline did not inhibit macrophage migration; and in thirteen experiments with synovium from an arthritis produced by injection of urate crystals only one showed significant inhibitory activity on macrophages. In contrast nineteen of twenty-five antigen challenged joints produced migration inhibitory factor detectable in the culture supernatants. Inhibition ranged from 20 to 87 per cent with a mean of 31·7±4·3 per cent. The migration inhibitory factor in these fluids was non-dialysable and was eluted with an albumin marker from Sephadex G-200. The finding that a macrophage migration inhibitory agent is produced in the course of antigen-induced synovitis is consistent with the postulated role of cellular immunity in the synovial lesion.