H&E histology and mixed chimerism. A–C, Graft and host tissue components in a syngeneic transplant combination (>130 d): syngeneic (B6) graft heart (*), cross-section including both ventricles, with associated body wall, including sternum with cellular hematopoietic bone marrow (***), attached muscles have (expected) myofiber loss (atrophy), and scattered mineralized fibers (A); host B6 heart (*) longitudinal (sagittal) section including right and left ventricles (B); graft heart base (rostral to A) polyethylene cuff tube- (yellow (*)), graft thymus (**) with distinct medulla and cortex (C), attached sternum (***) and musculature. (D–F) Graft (BALB/c) heart and host (B6) tissue components in an allogeneic CoB-treated transplant combination (>130 d): graft (BALB/c) heart with great vessels and cuff, attached graft sternum (****) and ribs (***) with hematopoietic bone marrow, graft thymus with distinct medulla and cortex (D); graft sternum bone marrow (E) and host sternum bone marrow (F); active hematopoiesis in both indicates viability of the VBM component. (G) Donor-specific chimerism is observed in peripheral blood mononuclear cells (>130 d) of C57BL6 recipients of a Balb/c allograft treated with CoB indicating viability of the VBM component of the chest wall allograft (data obtained from 2 to 3 animals).