Dolph Houben

141 Viability and immune response to VCA 7 Systemic response to allotransplantation We determined total white blood cells (WBC), lymphocytes, eosinophils, monocytes, neutrophils and red blood cell (RBC) counts to assess the systemic immunological state of the pigs. Pre- operative cell counts were obtained pre-operative, and 1, 2, 4, 6, 10, and 20 weeks after transplantation. Pre-operative measurements did not show a statistical difference between the two intervention groups. Immunosuppression was started intra-operatively. We observed an increase of total white blood cell counts, as well as lymphocyte, eosinophil, and neutrophil levels during the first postoperative week in both groups. White blood cells returned to baseline levels one week later. Lymphocyte, eosinophil, and neutrophil levels also decreased after the first week but did not directly return to pre-operative levels in either group (Fig. 2). The decrease in blood cell counts after one week is consistent with expected effect of drug immunosuppression. Two weeks after the transplantation, immunosuppressive therapy was stopped, and the central line surgically removed. We observed a slight increase of total WBC and neutrophil counts after this second intervention. None of the animals showed clinical signs of infection. Seromas at the surgical site were common and resolved spontaneously. Four weeks postoperatively, eosinophil levels were significantly elevated in the ligated AV-bundle group (p=0.03). Between the 4 th and 6 th week the total WBC, eosinophil and neutrophil levels decreased, and remained stable thereafter. Total WBCs, neutrophils, eosinophils, lymphocytes, and monocytes returned to pre-operative levels from the 6 th week until the end of the survival period (Fig. 2). Additionally, we quantified IL1A, IL1B, TNF, INFG, IL2, IL4, IL6, IL8, IL10, IL12, IL18 and GM- CSF/CSF2 levels in peripheral blood at the same periods (Fig. 3). In both groups, cytokine levels increased in the first week. All cytokine levels decreased after the first week and returned to pre- operative levels (not detectable levels) between the 4 th and 6 th week and remained stable thereafter (Fig. 3). No differences in systemic immune response were found between the groups for any cytokine. Taken together, the analyses of total blood cell counts and cytokine measurements did not demonstrate substantial immune responses to the allotransplant after 4-6 weeks.