This project was designed to investigate the application of bone marrow transplantation to a progressive and ultimately fatal systemic autoimmune disease. Male (NZW x BXSB)F1 (W/BF1) mice develop acute systemic autoimmune disease characterized by degenerative coronary vascular disease (CVD) with myocardial infarctions, hypertension, thrombocytopenia, glomerulonephritis, and persistently elevated levels of circulating immune complexes. After preliminary studies established the onset of disease between 10 and 12 weeks of age, 6- to 8-week-old male W/BF1 mice were targeted for transplantation with either T-cell-depleted bone marrow or purified hematopoietic stem cells from haploidentical B6C3/F1 mice. Posttransplantation flow cytometric analysis of splenocytes demonstrated donor phenotypes in W/BF1 recipient mice that had received T-cell-depleted marrow or hematopoietic stem cell preparations (lineage negative, CD71 negative) from B6C3/F1 donors. Survival of W/BF1 mice transplanted with bone marrow from normal B6C3/F1 donors was very high, and assessment at 100 days after transplantation revealed reduction in onset and severity of disease. Autoantibodies to cardiolipin and double-stranded DNA were markedly reduced to levels present in normal mice. Immunohistochemistry of heart and kidney tissue revealed significant amelioration of degenerative CVD and glomerulonephritis in the majority of W/BF1 recipients of marrow transplants from B6C3/F1 donors. All engrafted W/BF1 mice displayed normal immunologic competence 100 days posttransplantation. Biol Blood Marrow Transplant 2000;6(5):513-22.