Rheumatoid factors in natural retrovirus infections of the cat and cattle

The occurrence of IgM-rheumatoid factors (RFs) was investigated in natural retrovirus infection of cats with feline leukaemia virus and of cattle with bovine leukaemia virus. IgM-RFs of polyclonal character were detected. No significant differences were observed between the amounts of IgM-RFs in the retrovirus-infected animals and their respective controls.