Our results showing anti-MPO and anti-DNA autoantibody production by B cells recovered from lungs of cSiO2-exposed female BXSB mice mirror those in cSiO2-exposed MRL/MpJ mice, a genetically distinct lupus-prone strain for which anti-DNA IgG, but not anti-MPO IgM, are detected in supernatants of lung cell cultures (25). The gene discussed is MPO; the disease is systemic lupus erythematosus.