IgM rheumatoid factors in mice injected with bacterial lipopolysaccharides

Bacterial lipopolysaccharides (LPS) induced the formation of IgM rheumatoid factors (RF) in several strains of mice including athymic C57BL/6 nude mice, but not in the LPS-resistant C3H/HeJ mice. The RF induced by LPS reacted not only with murine IgG but also with IgG from cows, goats, guinea pigs, and humans. The kinetics of this RF response to injection of LPS were similar to those of antibody response against DNA and a hapten, dinitrophenyl (DNP), and to those of total IgM production. In addition, the RF activity of individual serum samples correlated significantly with levels of anti-DNA and anti-DNP antibodies and of IgM. Therefore, it is concluded that the induction of RF results from polyclonal antibody synthesis by B cells stimulated with LPS. This observation suggests that LPS or LPS-like substances may help to generate RF in patients with rheumatoid arthritis or with some infectious diseases.