Lung transplantation in the rat: histopathology of left lung iso- and allografts

The histopathology of pulmonary isografts and allografts in rats was investigated. During the first three days after transplantation the isografts showed scattered areas of exudate, containing polymorphonuclear leukocytes and macrophages, and a large number of type II alveolar cells with a highly pyroninophylic cytoplasm. One to two months later these pathological findings had completely disappeared. In contrast, the allografts were rapidly infiltrated with predominantly mononuclear leukocytes, from the second postoperative day onwards, eventually resulting in a more or less hemorrhagic and necrotic graft eight days after transplantation. Rat lung allografts are rejected faster than canine lungs, and more uniformly because of the use of inbred rat strains with defined histocompatibility mismatches. The rat model offers an advantageous model to study immunologic aspects of lung and heart-lung transplantation.