Synovitis associated with serum IgM rheumatoid factor arising spontaneously in 'Old English' rabbits

This paper reports the spontaneous development of synovitis in 'Old English' rabbits concurrent with serum IgM rheumatoid factor. Female rabbits developed lesions at a higher incidence than males (42% compared with 17%) and the pathology was of a more severe nature. In the female rabbits synovitis was associated with concurrent high serum IgM rheumatoid factor and high serum antibody levels to Pasteurella multocida. There was no histological evidence that the joints were directly infected.