Thermal inactivation and gradient studies of the active agent in rheumatoid arthritis.

Ten day embryonated eggs have been used for testing supernatants of pooled RA synovial tissues for the presence of the RA-active agent. A high thermal resistance of the agent was observed up to 40 min of heating both at 100 and 121 degrees C with complete loss of infectivity only after 60 min at 121 degrees C. The high thermal resistance at 121 degrees C suggested that the active agent does not depend on a double-stranded DNA or RNA. It probably has no protein component and has a minimal number of subunits for replication. The CsC1 ultracentrifugation identified a concentration of high infectivity at densities in the range of 1.440-1.490 g/ml in five experiments.