Immunological responses of the rat to Mycoplasma arthritidis.

Arthritis was produced in rats by the intravenous injection of Mycoplasma arthritidis. Metabolic inhibiting antibody and indirect hemagglutinating antibody could not be detected in the sera of arthritic or convalescent animals. Nonmurine species of mycoplasma were capable of inducing metabolic inhibiting antibody in the rat. A hypothesis based upon the possible occurrence of heterogenetic antigens common to M. arthritidis and rat tissue was brought forward to explain these findings. Complement-fixing antibody to M. arthritidis was detected 3 to 4 days after injection and subsequently rose to high levels, depending upon the severity of arthritis and number of organisms injected. Animals that had recovered from intravenous or subcutaneous inoculation with M. arthritidis were resistant to subsequent infections by the organism. Immunity could be passively transferred by the intravenous injection of convalescent serum. Adsorption of the convalescent serum with antigen greatly reduced the complement fixation titer but did not significantly alter the protective properties of the serum. The presence of complement-fixing antibody could not be related to the development of immunity. An avirulent strain of M. arthritidis and a strain previously classified as M. hominis type 2 were capable of inducing resistance to subsequent injection by virulent M. arthritidis.