Lipopolysaccharide induction of IgM antibodies to polyadenylic acid in normal mice

Lipopolysaccharide (LPS) is able to induce autoantibodies reversibly in normal mice. Single or multiple doses of LPS induced a rapid and dose-dependent rise in antibodies to Poly A from 113 ng to 590 ng/ml serum as determined by Millipore filter radioimmunoassay. The response peaked at day 3 and was over by day 21. No response was seen if the LPS was chemically inactivated or injected into genetically nonresponsive mice. Antibodies were specific for Poly A and were not induced by T cell mitogens. Sucrose gradient ultracentrifugation demonstrated only IgM antibody. Neonatal thymectomy altered neither the immunoglobulin class nor quantity of antibody. Neonatal splenectomy did not affect antibody class but reduced the amount produced. No free Poly A could be detected in circulation after LPS stimulation. These findings suggest that normal mice have B lymphocytes capable of limited and reversible autoantibody production.