Reduced tumor growth correlating with graft-versus-host disease (GvHD). [C57BL/6 × BALB/c]F₁ (H-2^b/d) mice received transplants of bone marrow from syngeneic F₁ donors (panels A,D,G,J, negative control group); allogeneic C57BL/6 (H-2^b) donors (panels B,E,H,K); or allogeneic BALB/c (H-2^d) donors (panels C,F,I,L), respectively. Original magnification × 100 used for histology (D-I). (A-C) Outgrowth of the BALB/c (H-2^d)-derived MethA fibrosarcoma (H-2^d) in the respective transplantation models (tumor size indicated by arrows). Inserts show manifestations of cutaneous GvHD with squamous skin changes in both allogeneic models (panels B-C). (D-F) Histology of tumors (H&E-staining) showed marked necrosis and adjacent mononuclear cell infiltrates (indicated by arrows) in recipients of allogeneic transplants (panels H-I). (G-I) Immunohistochemistry for CD8 of MethA tumor sections identified massive CD8⁺ cellular infiltrates in the border area of tumor necrosis (brown staining) in allogeneic transplant recipients (panels H-I). (J-L) Donor cell chimerism of CD3⁺ T cells on day 28 after BMT revealed by fluorescence-activated cell sorter (FACS) analysis after immunostaining for H-2K^d and H-2K^b.