Some histological features of canine cardiac transplants.

The cellular reaction in cardiac homografts was observed mainly in the perivascular areas and in the subepicardial and subendocardial layers. All the valvular structures were involved by the cellular infiltration, but the aortic and pulmonary cusp changes were less severe. Although the vascular changes seemed to be severe, yet, for unknown reasons, some vascular segments and consequently some myocardial areas were spared. The intermittent immunosuppressive therapy (azathioprine) seemed to have influenced the pathological changes; it did not completely prevent the rejection process, suggesting that better control of the host-versus-graft reaction could be obtained by continuous immunosuppression.