TGF β in the plasma from mice transplanted with MPZenNeo (○) and MPZenTPO (•) virus-infected bone marrow cells. Levels were measured using an enzyme linked immunoabsorbent assay (ELISA) kit (Genzyme, Cambridge, MA). Controls were plasma from MPZenNeo reconstituted mice collected 30 days (n = 5) and 155 days (n = 3) posttransplantation.