Variability in the induction of experimental arthritis: Yersinia associated arthritis in Lewis rats

Lewis rats of different microbiological status were studied for susceptibility to experimentally-induced Yersinia associated arthritis. Status A rats were serologically positive for Bacillus piliformis, Kilham rat virus and Toolan H-1 virus, whereas status B rats were serologically negative for these same microorganisms. When status A and status B rats were kept in the same room, incidence of arthritis was low (0-13% for status A rats and 27-33% for status B rats). When status B rats only were kept in different environments, increased incidence (up to 89%) of arthritis was observed. These findings suggest that the microbiological status of the host has an effect on the susceptibility to experimentally-induced arthritis. They call attention to the need for strictly defined conditions, including those of the host and the environment, in studies on experimental arthritides.