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Identification of an alternative CTLA-4 ligand costimulatory for T cell activation
K S Hathcock1, G Laszlo, H B Dickler
1Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Abstract:
Stimulation of T cell proliferation generally requires two signals: The first signal is provided by the T cell receptor binding to antigen, and the second signal or costimulus is provided by a different receptor-ligand interaction. In mouse and human, the CD28-B7 interaction has been identified as a source of costimulatory signals. We have identified a cell surface molecule (GL1) that is distinct from B7 and abundantly expressed on activated B cells. On activated B cells GL1, rather than B7, is the predominant ligand for the T cell-activation molecule CTLA-4. GL1 provides a critical signal for T cell-dependent responses in vitro and in vivo.