Review Article

B7-H4 Pathway in Islet Transplantation and β-Cell Replacement Therapies

Figure 2

The outcome of transplantation is determined by cosignalling. Full T-cell activation requires two signals. The first is antigen-specific recognition of TCR and alloantigen presented on MHC. The second is costimulation which can be positive or negative. In the presence of positive cosignalling (such as with CD28), T-cell proliferation occurs. These activated T cells attack the donor graft and results in graft rejection. One the other hand, the activated T-cell response is terminated in the presence of negative co-signalling (such as with CTLA-4) which protects the graft from destruction.
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