Role of Biological Mimicry in the Pathogenesis of Rat Arthritis Induced by Mycoplasma arthritidis.

Complement fixation (CF), immunofluorescence, and agar gel double-diffusion tests were used to demonstrate an antigenic relationship between rat tissues and Mycoplasma arthritidis. Rabbit antisera against six strains of M. arthritidis exhibited positive reactions in the CF test with an ethyl alcohol-saline extract of rat muscle, whereas only 6 of 18 antisera against other Mycoplasma species were positive. With the use of gel diffusion techniques, absorption of various M. arthritidis antigens with antiserum against rat muscle removed at least one precipitin band when the absorbed mycoplasma antigens were reacted against homologous antisera. Rabbit antiserum against M. arthritidis was conjugated with fluorescein isothiocyanate and reacted against frozen sections of muscle tissues of various animals. As controls, unlabeled normal rabbit serum and rabbit anti-M. arthritidis serum were included to determine the specificity of the reaction. Rat, hamster, and mouse skeletal muscle exhibited specific fluorescence, whereas chicken, beef, frog, and turtle muscles exhibited no specific fluorescence. Mice injected at birth with rat lymphocytes were found to be more susceptible to subsequent infection by M. arthritidis than were normal mice or mice injected at birth with mouse lymphocytes. These results indicate the occurrence of a heterogenetic antigen(s) common to M. arthritidis and rat tissues. Preliminary evidence suggests that this heterogenetic antigen(s) may enable the mycoplasmas to become established in their host.