Etiopathogenesis of rheumatoid arthritis-like disease in MRL/1 mice: II. Ultrastructural basis of joint destruction.

MRL/1 mice develop a spontaneous hindlimb arthropathy characterized by proliferation of synovial cells and by dissociation between early destruction of articular tissue and the presence of inflammatory cell infiltration. To characterize the ultrastructural details of the synovial cells of these mice, knee joints from MRL/1, MRL/n, and BALB/c mice were examined by light and electron microscopy. Since the proliferating synovial cells of MRL/1 mice resemble the previously described proliferative synovial cells seen in histopathologic specimens from early rheumatoid arthritis, further study of these cells may provide new insights into the pathogenesis of early joint tissue destruction in human rheumatic disease.