Expression of metabolism-inhibition antibodies against Mycoplasma arthritidis in rats

Shared antigens between Mycoplasma arthritidis and rat tissues may be responsible for the lack of metabolism-inhibition (MI) and other neutralizing antibodies in rats with M arthritidis-induced arthritis. We were not able to confirm such antigens or to detect cross-reacting antigens between M arthritidis and rat lymphocytes, thymocytes, and muscle tissue. Antisera of rabbit origin to rat lymphocytes, thymocytes, and skeletal muscle reacted by ELISA with M arthritidis only when the mycoplasmal antigens were prepared from organisms grown in medium containing horse serum. Such activity could be completely absorbed by horse serum. These antisera to rat tissues also failed to react by radioimmunoprecipitation with M arthritidis surface antigens. In addition, antibody activity against homologous antigens could not be absorbed by M arthritidis. Similarly, antisera of rabbit origin against M arthritidis failed to react by ELISA specifically with rat lymphocytes, thymocytes, and skeletal muscle or to react by radioimmunoprecipitation with 125I-labeled rat lymphocyte antigens. These rat tissues could not specifically absorb antibodies against M arthritidis from antisera of rabbit origin. These findings suggest that the lack of MI antibodies in rats probably can not be explained by rat tissue antigens that cross-react with M arthritidis MI antigens. Finally, antisera of rat origin against M arthritidis and other rat tissue components failed to block rabbit MI activity against M arthritidis, thus arguing against steric hindrance as a means of preventing recognition of MI antigens.