Monoclonal rheumatoid factors from B6-lpr/lpr mice

Monoclonal rheumatoid factors (MoRF) were prepared from autoimmune B6-lpr/lpr mice to investigate the influence of strain background on the specificity of these autoantibodies. Using screening assays for binding to heterologous rabbit IgG, four IgM MoRF were obtained. Three of these antibodies showed a broad pattern of reactivity with IgG antigen, binding BALB/c myeloma IgG1, IgG2a and IgG3 as well as heterologous IgG. One of the antibodies, however, had a distinct form of IgG interaction and was without reactivity with any of the BALB/c myelomas tested. None of the antibodies had significant reactivity with IgG2b. These results suggest common features of B6-lpr/lpr rheumatoid factor (RF) specificities, some of which may be shared by comparable products derived from MRL-lpr/lpr mice. Comparison of these antibodies with those in other reported series suggests that the background genome as well as the nature of the inducing mechanisms may affect the specificity of RF as well as their pathogenetic role.