Development of autoantibodies to intracellular molecules is a universal feature of autoimmune diseases and parallels onset of chronic inflammatory pathology. Initiating antigens of disease-specific autoantibody responses are unknown. We previously showed that the major targets of autoantibodies in scleroderma are centrosomes, organelles involved in mitotic spindle organization. Here we show that centrosome autoantibodies are induced in mice by mycoplasma infection. The centrosome-specific antibody response involves class switching of preexisting IgM to IgG isotypes, suggesting a T cell-dependent mechanism. The antibody response spreads to include additional intracellular targets, with newly recruited autoantibody specificities arising as IgM isotypes. Antibiotic treatment of mice prevents autoantibody development. Centrosome autoantibodies may provide an aetiological link between infection and human autoimmunity and suggest novel therapeutic strategies in these disorders.