Arthritis in rats produced by pleuro-pneumonia-like organisms.

Attempts to produce in animals conditions resembling various rheumatic diseases have been numerous and have employed a wide variety of agents. Such work has usually had as its object the investigation of the part played by a certain factor in the causation of rheumatic conditions or the provision of animal subjects to test the efficacy of therapeutic agents. The work reported here was undertaken with the latter object in view. The agent selected was a strain of pleuro-pneumonia-like organism (PPLO). This group has been surveyed by Sabin (1941) and Dienes (1945) who deal particularly with their morphology and characterization. There seems to be no evidence for associating rheumatoid arthritis with PPLO infection; attempts to isolate the organism from cases of rheumatoid arthritis have been unsuccessful (Preston, 1942). However, PPLO has been isolated from spontaneously occurring polyarthritis in rats; injection of this material into rats has been said to produce progressive changes of an arthritic nature in the joints. (Cf. also Collier and Staverman, 1940.) Work with this organism, in rats and mice, has been reviewed by Findlay (1946). Detailed comparisons of a number of strains of PPLO isolated from animals have been made by Klieneberger (1938, 1940). One such strain, designated " L4 ", is characterized by the production of abscesses, adenitis, and arthritis; this strain has been serologically identified with those employed by earlier workers on experimental arthritis in rats using PPLO. Tripi and Kuzell (1947, 1949) used a known L4 strain of PPLO to produce experimental arthritis in rats. Sabin (1939, 1940) and Preston (1942) describe pathological changes occurring in the joints of experimental animals injected with cultures of PPLO. Sabin regards the condition produced in mice as resembling human rheumatoid arthritis in its clinical course and pathology, but Preston (1942) finds that the changes occurring in rats more closely resemble pyogenic joint infections in man.