Intrigued by this activation of T cells against a tumor, Allison and several other researchers spent more than a decade trying to deepen their understanding of the protein’s function. As all the earlier experiments had shown, they found that CTLA4 was a system to prevent horror autotoxicus; it was a T cell’s trigger lock. Under normal circumstances, when CTLA4 on activated T cells meets its cognate binder, called B7,III that is present on the surface of cells of the lymph nodes, where T cells mature, the safety switch is turned on. The maturing T cells are disabled from attacking the self but
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