Aim: Liver sinusoidal endothelial cells (LSECs) have been implicated to play a role in the induction of liver allograft rejections. Here, we studied the clinical consequences of preformed LSEC-reactive antibodies and their functional capacity in modulating T-cell responses.
Methods: Pre- and posttransplant sera and T lymphocytes from 95 liver transplant patients were used in this study. LSECs were isolated from a normal healthy liver. Binding of antibodies to LSECs was detected using flow cytometric analysis. To study whether LSEC antibodies facilitated cell-mediated immunity, a mixed cell culture (MCC) assay was used. Cytokines in the supernatant of MCC were also measured by enzyme-linked immunosorbent assay. Immunohistochemical staining on liver biopsy sections was performed to detect deposition of immunoglobulins in LSEC during rejections.
Results: Significantly higher numbers of patients with rejections had LSEC antibodies (35/50, 70%) compared with 8/45 (18%) without rejections (P < .0001). Purified fractions of LSEC antibodies induced the expression of the costimulatory marker CD86 on LSECs. Significantly higher numbers of patients with LSEC antibodies and rejections had an increased proliferation of T cells and markedly decreased levels of transforming growth factor (TGF)-beta in the MCC as compared with those without antibodies and rejections (P < .0001, P < .0001, respectively). Deposition of antibodies in LSECs during rejection episodes was observed in the biopsies of patients with LSEC antibodies but not in those without LSEC antibodies.
Conclusion: Our data suggest that antibodies to LSEC may facilitate acute liver allograft rejections by down-regulating the immune modulating cytokine TGF-beta and thus up-regulating alloreactive T-cell proliferation.