OUTLINE: This is a multicenter study. Patients undergo leukapheresis to collect white blood cells which are incubated with donor bone marrow cells in the presence of anti-B7.1 and anti-B7.2 antibodies for 36 hours. Patients receive total body irradiation twice daily on days -6 to -3, cyclophosphamide IV daily on days -2 and -1, and methylprednisolone IV every 12 hours for a total of 4 doses on days -2 to 0. Patients are infused with the treated donor bone marrow on day 0. Patients then receive methotrexate IV on days 1, 3, 6, and 11 and leucovorin calcium IV 24 hours after each dose of methotrexate every 6 hours for 3-8 doses each time. Patients also receive cyclosporine IV or orally twice daily on days -2 to 100. Patients are followed every 2 months for 1 year.