(Fig. in allogenic non-immunosuppressed group B (splenocytes: MHC class I – day 0 (93%7% ) vs day 30 (66%7%),p= 0.02, MHC class II – day 0 (105%3% ) vs day 30 (83%5%),p= 0.003; B-cells: MHC class I – day 0 (83%5%) vs day 30 (55%6%),p= 0.003, MHC class II – day 0 (101%1%) vs day 30 (79%6%),p= 0.006; T-cells: MHC class I – day 0 (71%7%) vs day 30 (49%5%),p= 0.04). No free clusters of immunoglobulin G deposition were detected in any experimental group. == Conclusion == Arterialized venous allografts induce strong donor-specific anti-MHC class I and anti-MHC class II antibody production with subsequent immune-mediated destruction of these allografts with no evidence of immunoglobulin G deposition. Low-dose tacrolimus suppress the donor-specific antibody production. == Introduction == There remain a group of vascular patients with critical leg ischemia who SID 3712249 are not suitable for the use of greater saphenous vein or prosthetic grafts in peripheral vascular reconstruction. In specific indications, allogeneic veins are used in these patients.[1]However, allogeneic veins are immunogenic because of the expression of both class I and class II major histocompatibility complex (MHC) antigens on their wall cells.[2]These antigens stimulate immune responses in the host that lead to the destruction of the allovenous wall structure. The rejection is represented by graft thrombosis or by graft dilatation with the risk for graft rupture.[3],[4] SID 3712249 One possibility for increasing the patency rates of venous allografts is the use of immunosuppressive drugs.[5]However, immunosuppression is not routinely used in clinical practice.[1]When immunosuppression is used, cyclosporine A is the most frequently administered drug to patients with allovenous bypasses.[6][8]. However, recently published data confirmed considerable vascular side effects SID 3712249 from cyclosporine A.[9],[10]Contrary to cyclosporine A, tacrolimus, a newer and more potent immunosuppressive drug routinely used in renal and liver transplant patients, showed significantly advantageous characteristics related to hypertension, dyslipidaemia, and renal function in transplant patients.[9]Moreover, tacrolimus seems to be a promising compound in a new generation of coronary drug eluting stents.[11]. In our previous experiments, we used the rat ileolumbar vein to abdominal aorta transplantation model to study the effect of low-dose tacrolimus immunosuppression on rejection changes and adaptation of venous allografts to arterialisation in rats. Tacrolimus inhibited cell-mediated rejection, and the immunosuppressed alloveins developed characteristic signs of the wall remodelling process observed in syngeneic arterialised veins.[12]. However, the significance of antibody-mediated rejection in chronic vascular rejection and consecutive failure of transplanted organs seems to be more and more important.[13]Moreover, the production of donor-specific antibodies against the major histocompatibility complex (anti-MHC) in dogs was clearly connected with venous allografts thrombosis.[4]. In the present study, we determined the following parameters: (1) the presence and dynamics of alloantibodies recognizing MHC complexes on Brown-Norway (BN) splenocytes, quiescent BN splenic B-cells and SID 3712249 T-cells in the sera of Lewis (LEW) recipients of BN iliolumbar vein grafts under low dose tacrolimus immunosuppression; and (2) the presence of immunoglobulin in the rejected allovein wall. For this purpose, we screened for the presence of Mouse monoclonal to GST donor-specific anti-MHC class I and II antibodies in recipients sera that was obtained previously in our Brown-Norway to Lewis rat model of allovenous arterialisation.[12]. == Materials and Methods == == Ethics statement == The SID 3712249 principles of laboratory animal care were followed and all rats were maintained according to the National Institute of Health Guidelines. Ethical approval by a local ethical committee of the Institute for Clinical and Experimental Medicine was obtained for this study. == Animals == Adult male inbred Brown-Norway (BN; RT1n) and Lewis (LEW; RT1l) rats were obtained from Charles River (Sulzfeld, Germany). Male LEW rats (N = 23, 200340 g) were used as recipients of allogeneic or syngeneic iliolumbar vein grafts. Male BN rats (N = 9, 220300 g) were used as donors of allogeneic iliolumbar vein grafts. Male LEW rats (N = 3, 280300 g).