Distant procurement of organs for transplantation requires satisfactory preservation to reduce injury during ischemia and the initial phase of reperfusion. We have studied the mechanism of reimplantation injury after unilateral lung transplantation in isogeneic Fisher rats. The heart and lungs were removed en bloc from donor rats and preserved at 4 degrees C. After 5 hours the left lung was transplanted into a recipient. Radiographic and histologic evidence of pulmonary edema in the transplanted lung at 24 hours confirmed the presence of lung vascular injury. In five rats we performed bronchoalveolar lavage (BAL) of both nontransplanted and transplanted lungs at 24 hours posttransplant, immediately after the animal was killed. Results were compared with five normal control lungs. The results showed not only significantly greater number of cells from transplanted lungs compared with nontransplanted and control lungs but cell profiles showed much greater percentages of neutrophils (mean +/- SD) from transplanted (76.8% +/- 13%) compared with nontransplanted (2.8% +/- 3.1%) or control (0.8% +/- 0.8%) lungs. In seven other rats we measured BAL neutrophil activity with stimulated luminol chemoluminescence from transplanted left and nontransplanted right lungs 24 hours after unilateral left lung transplantation. Results (expressed as millivolt X 10(3) neutrophil +/- SD) showed significantly greater activity from transplanted (2.8 +/- 1.7) compared with nontransplanted (0.72 +/- 0.6) lungs. Reimplantation injury of the lung is characterized by pulmonary sequestration of neutrophils, and these cells may play a primary role in mediating vascular damage.