Immunological response of rats to Mycoplasma arthritidis

A sensitive assay for titration of antibodies which inhibit the metabolism of arginine by M. arthritidis was developed. Sera collected from rabbits immunized with M. arthritidis inhibited arginine metabolism when diluted 1:1600. The addition of fresh guinea pig serum enhanced the metabolic inhibition (MI) titer at least sixteen fold while heated guinea pig serum did not affect the titer of the rabbit antiserum. It was shown that rats did not produce detectable metabolic inhibiting antibodies to M. arthritidis, but did produce complement fixing antibodies in high titers. Preliminary experiments disclosed that uninoculated rats could be passively protected against an intravenous challenge of live M. arthritidis when given serum from rats that have recovered from polyarthritis. The rat serum used had a high titer of complement fixing antibodies and no detectable MI antibodies. Rats were injected intravenously with varying numbers of M. arthritidis. Rats inoculated with the larger doses of organisms developed polyarthritis to a greater extent than those injected with smaller doses. It was shown that complement fixing antibody occurred in the sera of rats inject with M. arthritidis within three days after inoculation. Sera from rats which developed polyarthritis general fixed complement at a greater dilution than sera of rats which did not develop polyarthritis. It was also shown that rats which ha recovered from polyarthritis were resistant to intravenous challenge with M. arthritidis. Only one of fourteen rats inoculated intravenously with M. arthritidis developed polyarthritis when challenged.