Immunoregulatory role for a public IgM idiotype in the induction of autoimmune diseases in Mycoplasma pneumoniae infection

Mycoplasma pneumoniae (MP) infection is associated with the emergence of various autoimmune disorders and autoantibody production. The most common autoantibodies induced are of anti-I specificity and express cold agglutinin (CA) activity. However, the mechanisms by which the microbial infection triggers the appearance of these autoantibodies are still unknown. To investigate these mechanisms, we used BALB/c mice as experimental models. In this paper, we show that BALB/c mice polyclonal antisera to MP react with human CA IgMs, and reciprocally, that BALB/c mice polyclonal antisera to human IgM CA react with MP. However, antibodies directed against MP and against CA IgM triggered by both immunizations represent two separate sets of antibodies. This was also confirmed using monoclonal antibodies derived from the immunized mice. Among these MAb we selected a monoclonal antibody MAb1D3 which reveals a cross-reactive idiotope (CRI) shared by human CA and other MIgMs with various autoantibody activities (anti-MAG and anti-IF). The CRI defined by MAb1D3 is a recurrent interspecies idiotope that is expressed by post infectious IgM antibodies to MP. Hence, we present in this study new data showing that the concomitant appearance of CAs and anti-MP IgM antibodies during acute MP infection is the consequence of a common idiotypic regulation of antibodies to infectious and to self antigens. (C) 2010 Elsevier B.V. All rights reserved.