Arthritogenic effects of Mycoplasma arthritidis T cell mitogen in rats.

The intraarticular injection of Mycoplasma arthritidis T cell mitogen (MAM) produced significant joint swelling with inflammation in DA rats. Histologic examination of the joint initially showed edema below the synovial surface layer with light polymorphonuclear and focal lymphoid cell infiltration. Widespread but incomplete shedding of the surface layer of the synovial membrane and hypertrophy and hyperplasia of the subsynovium with fibroblasts and macrophages were observed subsequently. The hyperplastic process began to resolve by Day 5 and almost completely disappeared by Day 7 with healing of the surface layer, leaving virtually no trace of the preceding acute episode. Arthritis in animals with previous adjuvant induced arthritis was not exacerbated by the intraarticular injection of MAM.