P>The expression of TfR/CD71 in T-cell surface plays a pivotal role in T-cell activation and proliferation. Anti-human-TfR monoclonal antibody could be used as an immunosuppressant in transplant therapy because of their potential to suppress T-cell responses to alloantigens. We therefore examined the feasibility of an anti-human-TfR chimeric antibody (D2C) in suppression of T-cell activation in vitro and graft-versus-host reaction (GVHR) in animals. D2C is a chimeric antibody produced by introducing the human Fc fragment. This antibody showed low antigenicity but high suppressive effect manifested by high potency to block the activation and proliferation of lymphocytes in response to alloantigens. D2C also showed capability to mediate complement-dependent cytotoxicity, which could be correlated with TfR expression in peripheral blood mononuclear cells (PBMCs). Importantly, administration of D2C significantly prolonged survival time of nude mice transplanted with human PBMCs when compared with that of control IgG-treated animals (61.2 +/- 4.46 vs. 22.1 +/- 5.5 days), which is associated with inhibited GVHR characterized by decreased interleukin-1 and tumor necrosis factor alpha production derived from transplanted PBMCs. Human-TfR chimeric antibody such as D2C could be a valuable option for the treatment of acute form of graft-versus-host disease.