Pathology of acute graft-versus-host disease in the dog. An autopsy study of ninety-five dogs.

The morphology of graft-versus-host disease (GVHD) in canine radiation chimeras was studied by examination of autopsy tissue from 95 dogs including: 1) 13 healthy, untreated dogs; 2) 9 dogs given 1200 R total body irradiation and no marrow infusion; 3) 17 dogs given 1200 R and autologous marrow infusion; 4) 25 dogs given 1200 R and hemopoietic cells from dog-leukocyte-antigen (DLA)--identical littermates; and 5) 31 dogs given 1200 R and nonidentical DLA hemopoietic cells. Some of the dogs in Groups 3--5 received a postgrafting methotrexate (MTX) regimen of 0.25--0.5 mg/kg body weight on Days 1, 3, 6, and 11 and once weekly until Day 102. Prominent lesions were found in the small and large intestines, skin, and liver of dogs with allogeneic grafts. Skin lesions consisted of lymphocytic infiltrates of epidermis with necrosis of basal epidermal cells progressing to denudation. Gut lesions consisted of mucosal destruction progressing from crypt abscess formation to denudation. Liver lesions consisted of portal triaditis, plasmacytic and lymphocytic infiltrates, necorsis and atypia of small bile ducts, and scattered individual hepatocyte necrosis. These lesions were differentiated from changes caused by irradiation and MTX and were deemed characteristic of GVHD. The overall severity of GVHD lesions was less in the identical DLA group than in the nonidentical DLA group, and also less in dogs treated with MTX than in those not given MTX. The degree of lymphoid depletion in the lymph nodes, spleen, and intestinal lymphoid tissue was very similar in dogs with autologous and allogeneic grafts at comparable survival times. No specific evidence of pancreatic or renal involvement in GVHD was discovered.