Introduction: It is hypothesized that IgM antibodies to oxidized LDL are anti-atherogenic. Myeloperoxidase from plaque-infiltrating neutrophils catalyzes the production of hypochlorite (HOCl), which oxidizes LDL. Here we study the IgM response to HOCl-modified LDL in comparison to titers of T15 clonotypic natural antibodies.
Methods: Plasma of LDLR(-/-) mice fed a normal chow or high-fat diet was obtained after 6 and 16 weeks. The IgM responses to HOCl-modified LDL and T15 clonotypic natural IgM antibodies were measured by ELISA.
Results: The IgM levels in response to HOCl-modified LDL increased dramatically in the atherosclerotic group after introduction of the high-fat diet, but not in mice on normal chow. The natural IgM T15 clonotypic antibody titers revealed a more moderate increase during atherogenesis.
Conclusion: Our results show that during atherogenesis there is a strong induction of IgM antibodies to HOCl-modified LDL particles. Whether these induced IgM antibodies are pro- or anti-atherogenic remains to be established.