Moreover, the selected strains develop clinical and immunological features and incorporate genetic susceptibility relevant to multiple silica-linked diseases: MRL mice develop delayed lupus nephritis, whereas their MRL/lpr congenic counterparts develop aggressive kidney disease and RA-like arthritis (21); a subset develop anti-myeloperoxidase (MPO) autoAb similar to those observed in ANCA vasculitis (22). The gene discussed is MPO; the disease is arthritic joint disease.