Oligoclonality of rheumatoid factors arising spontaneously in lpr/lpr mice.

Rheumatoid factors (RF) from individual mice of the MRL/lpr and C3H/lpr strains were examined with regard to target specificity and heavy chain class expression. It was found that MRL/lpr-derived RF preferentially recognize IgG2a target antibodies while C3H/lpr-derived RF exhibit a broader range of cross-reactivity. IgM RF represent only a minor proportion of the RF response in both strains. The IgG2a-specific RF produced by the lpr strains were found to consist of relatively equal proportions of IgG1, IgG2b, IgG3, and IgA antibodies. However, most of the RF produced by a single individual expressed the same heavy chain class and antigen-binding specificity. These results indicate that within an individual lpr mouse, circulating RF are derived from extensive expansion of a limited number of antigen-activated precursors.