The demonstration that rhNPM bound to cardiolipin (CL) in vitro and increased the CL-binding activity of a WB-derived aCL monoclonal antibody indicates that NPM can interact with CL to form SLE-related immunogenic particles that might be responsible for the concomitant production of anti-NPM and aCL antibodies. The gene discussed is NPM1; the disease is systemic lupus erythematosus.