Concordant lung xenograft rejection in a hamster-to-rat model.

This study was conducted to investigate the functional and morphological aspects of orthotopic lung xenograft rejection in a concordant hamster-to-rat donor-recipient species combination. By postoperative day (POD) 3, allotransplanted grafts demonstrated good aeration, but infiltrates were seen in all the xenotransplanted lungs. Antihamster lymphocytotoxic antibody titers increased to 5.2 +/- 1.1 by POD 3 (P < 0.05 vs POD 1) and reached 7.0 +/- 0.8 by POD 5 (P < 0.05 vs PODs 1 and 3). The CD4+/CD8+ ratio in peripheral blood lymphocytes increased significantly on POD 3 (P < 0.05 vs untransplanted), but decreased by POD 5 (P < 0.05). Histologically, on POD 3 the xenotransplanted grafts were characterized by perivascular cellular infiltrates and edema. Cytologically, the cells consisted of small round lymphocytes, monocytes, and occasional neutrophils. Immunohistochemical analysis showed heavy IgM and C3 deposits in the vascular endothelium, without any IgG deposits. Allotransplanted grafts showed moderate W 3/25 + (28.3 +/- 17.3%) and MRC OX8 + (38.7 +/- 0.7%) cellular infiltrations on POD 3, but ED1 + (8.0 +/- 3.7%) cells were rare. Conversely, in the xenotransplanted grafts, ED1 + (34.2 +/- 16.4%) cells were more prevalent than MRC OX8 + (18.1 +/- 16.5%) cells on POD 3, at P < 0.01 and P < 0.05 vs allograft, respectively. These results indicate that both antidonor antibodies and macrophages/monocytes play an important role in the concordant lung xenograft rejection.