[Pathological study of Streptococcus faecalis antigen-induced arthritis in New Zealand white rabbits].

The pathological examination of the rabbit knee joint with antigen-induced arthritis produced by heat-killed Streptococcus faecalis (Str. faec.) as antigen was carried out. Macroscopically, there were findings of acute inflammation about five hours after the injection. Histopathologically, very remarkable acute exudative inflammation was seen 48 hours later. This supported the picture of Arthus reaction. The Arthus reaction disappeared with time, and this supported the view of delayed-type hypersensitivity three weeks later. After that, an obvious chronic inflammation was admitted in 10 weeks. This resembled the histopathological feature of rheumatoid arthritis (RA) when these findings are summarized. It was suggested that arthritis produced by Str. faec. progresses from an acute condition to a one with time. As mentioned above, it thought that Arthus reaction of both immediate hypersensitivity and delayed-type hypersensitivity are necessary in the occurrence of this arthritis.