O303* Aims: To establish the effect of intravenous polyclonal immunoglobulins (ivig) on the incidence of acute rejection after liver transplantation and on dendritic cell (dc) function. Methods: As a model to study the influence of ivig on acute rejection, we analyzed a group of liver transplant recipients treated with prophylactic intravenous infusions of an anti-hepatitis b surface immunoglobulin preparation (anti-Hbs Ig, Hepatect®, Biotest Pharma GmbH, Germany) to prevent infection of the liver graft with hbv. Of the 216 recipients of a primary liver graft transplanted in our center between 1989 and 2002, forty were treated with anti-hbs Ig. In a retrospective analysis, the cumulative incidence of acute rejection of these patients was compared to recipients with hcv-infection (n=29), and to recipients without viral hepatitis (n=147), which both were not treated with any polyclonal Ig. Morever, immature dc were isolated by immunomagnetic selection from the blood of liver transplant recipients treated with anti-hbs Ig, or with hcv-infection, and of healthy individuals, and their capacity to stimulate allogeneic t-cell proliferation was determined. In addition, the influence of anti-HBs Ig on in vitro maturation of dc from healthy individuals was determined. Results: The cumulative incidence of acute rejection in hbv-infected liver transplant recipients treated with anti-hbs Ig was significantly lower (13%; p=0.01) as compared to recipients without viral hepatitis (34%). In contrast, hcv-infected recipients had a similar incidence of acute rejection (31%) as compared to recipients without viral hepatitis in multivariate Cox-regression analysis, treatment with anti-HBs Ig was, independently of other risk factors, associated with a reduced incidence of acute rejection (Relative Risk compared to recipients without viral hepatitis = 0.36; 95% ci=0.14-0.91; p=0.03). During the first two weeks after transplantation, the patients treated with anti-HBs Ig had high anti-HBs Ig concentrations in their serum (median peak levels: 3.5 mg/ml; range: 1.9 - 10.6). Therefore, we postulated that the reduced incidence of acute rejection in these patients might be due to a suppressive effect of anti-HBs Ig on dc-function. We found that DC obtained from HBV-infected recipients during anti-HBs Ig treatment had a strongly reduced capacity to stimulate allogeneic T-cell proliferation as compared to dc isolated from HCV-infected liver transplant recipients or from healthy individuals. In addition, the presence of anti-HBs Ig, in concentrations similar to the peak serum concentrations reached in the patients, during in vitro DC-maturation resulted in DC with a significantly reduced capacity to stimulate allogeneic T-cell proliferation as compared to DC maturated in the absence of anti-HBs Ig (n=5; p<0.05). Flow-cytometric analysis revealed that the expression of the co-stimulatory molecule CD80 on DC maturated in the presence of anti-HBs Ig was significantly reduced (p=0.02), while induction of HLA-DR and CD86-expresion were unaffected. Conclusions: Immediate post-transplant treatment with a specific IVIG-preparation (anti-HBs Ig) is associated with a significantly reduced incidence of acute rejection in liver transplant recipients. This may be due to inhibition of the acquirement of allogeneic t-cell stimulatory capacity in their DC by the anti-HBs Ig. This type of ivig-preparations may be applicable as immusuppressive agents after organ transplantation.