T-cell activation by the CD28 ligand is required for cardiac allograft rejection in vivo

The roleof the CD28 receptor expressed on T-cells in organ graft rejection was investigated. Earlier studies have found that organ graft rejection depends notonly on the stimulation of the T-cell receptor/CD3 complex by foreign major histocompatibility complex (MHC)-encoded gene products, but also by other co-stimulatory signals that induce T-cell activation. The results showed that activation of T-cells by the CD28 ligand B7 is essential as a co-stimulatory event for the rejection of a MHC-incompatible cardiac allograft in vivo.