Some aspects of changed histopathologic appearance of acute rejection in cardiac allografts after prophylactic application of OKT3.

The histopathologic findings of therapy-requiring acute rejection in the cardiac allograft observed in endomyocardial biopsy specimens taken from patients under prophylactic administration of OKT3 show certain differences in comparison with the classic description of acute rejection. These differences are characterized above all by a distinctly reduced cellularity of the infiltrates, with a relative decrease of T cells, as well as edema and retrogressive changes, up to necroses of myocytes with marked fragmentation; some patients also have increased vascular reactions. Furthermore, an earlier occurrence of and an increased frequency of changes corresponding to the so-called lymphoma-like lesions ("Quilty" effect) were observed in patients who received immunosuppressive prophylaxis with OKT3. The changed histopathologic findings of therapy-requiring acute rejection under prophylactic application of OKT3 may, to a certain extent, explain the discrepant results reported by different transplant groups with respect to the frequency of rejection episodes and the time when the first episode of therapy-requiring rejection occurs after heart transplantation.