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From the * Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121; and The 4-1BB receptor is an inducible type I membrane protein and member of the tumor necrosis factor receptor (TNFR) superfamily that is rapidly expressed on the surface of CD4+ and
CD8+ T cells after antigen- or mitogen-induced activation. Cross-linking of 4-1BB and the T
cell receptor (TCR) on activated T cells has been shown to deliver a costimulatory signal to T
cells. Here, we expand upon previously published studies by demonstrating that CD8+ T cells
when compared with CD4+ T cells are preferentially responsive to both early activation events
and proliferative signals provided via the TCR and 4-1BB. In comparison, CD28-mediated
costimulatory signals appear to function in a reciprocal manner to those induced through 4-1BB
costimulation. In vivo examination of the effects of anti-4-1BB monoclonal antibodies (mAbs)
on antigen-induced T cell activation have shown that the administration of epitope-specific
anti-4-1BB mAbs amplified the generation of H-2d-specific cytotoxic T cells in a murine
model of acute graft versus host disease (GVHD) and enhanced the rapidity of cardiac allograft or skin transplant rejection in mice. Cytokine analysis of in vitro activated CD4+ and CD8+
T cells revealed that anti-4-1BB costimulation markedly enhanced interferon-
Department of Surgery, Emory University School of Medicine, Atlanta, Georgia 30322
production by
CD8+ T cells and that anti-4-1BB mediated proliferation of CD8+ T cells appears to be IL-2
independent. The results of these studies suggest that regulatory signals delivered by the 4-1BB receptor play an important role in the regulation of cytotoxic T cells in cellular immune responses to antigen.
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