Mixed cellular and humoral acute rejection in elective biopsies from heart transplant recipients

Acute cellular rejection in heart transplants is characterized by an active lymphocytic infiltration, whereas the humoral response shows complement deposits in myocardial tissue. Both reactions may produce hemodynamic compromise during the first months after orthotopic heart transplantation (OHT). The aim of this study was to estimate the coexistence of humoral rejection symptoms in the first posttransplant biopsy with mild/moderate cellular rejection as an additional prognostic factor.

The study group included 13 biopsies obtained from 11 men and 2 women of overall mean age of 52.6 +/- 5.3 years who displayed International Society for Heart and Lung Transplantation (ISHLT) mild/moderate rejection grades. The control group consisted of 11 biopsies obtained from 8 men and 3 women of overall mean age of 54.8 +/- 3.6 years with no signs of rejection. Complement deposits were determined immunohistochemically using anti-C4d antibodies (Quidel Corporation).

None of the control cases showed a positive reaction, whereas 3 men in the study group of mean age of 56.1 +/- 5.8 years revealed regional positive anti-C4d expression with cellular infiltrates. This expression occurred in all myocardial components adjacent to lymphocytic infiltrations. The survival rates were comparable in both the pure cellular versus the mixed rejection groups. The relative rate of grade 3 rejection in the posttransplantation period was increased among patients with mixed types of rejection.

The term "mixed acute rejection" should be applied to cases with coincidence of 2 forms of acute rejection. It seemed to be associated with more frequent grade 3 rejection processes upon long-term follow-up.