Fibrinogen-like protein 1 is a major immune inhibitory ligand of LAG3

• Published in: Cell Vol. 176; no. 1-2; pp. 334 - 347.e12
• Main Authors: Wang, Jun, Sanmamed, Miguel F., Datar, Ila, Su, Tina Tianjiao, Ji, Lan, Sun, Jingwei, Chen, Ling, Chen, Yusheng, Zhu, Gefeng, Yin, Weiwei, Zheng, Linghua, Zhou, Ting, Badri, Ti, Yao, Sheng, Zhu, Shu, Boto, Agedi, Sznol, Mario, Melero, Ignacio, Vignali, Dario A. A., Schalper, Kurt, Chen, Lieping
• Format: Journal Article
• Language: English
• Published: 20.12.2018
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2018.11.010

Lymphocyte-activation gene 3 (LAG3) is an immune inhibitory receptor, with major histocompatibility complex class II (MHC-II) as a canonical ligand. However, it remains controversial whether MHC-II is solely responsible for the inhibitory function of LAG3. Here, we demonstrate that fibrinogen-like protein 1 (FGL1), a liver-secreted protein, is a major LAG3 functional ligand independent from MHC-II. FGL1 inhibits antigen-specific T-cell activation and ablation of FGL1 in mice promotes T-cell immunity. Blockade of the FGL1/LAG3 interaction by monoclonal antibodies stimulates tumor immunity and is therapeutic against established mouse tumors in a receptor-ligand inter-dependent manner. FGL1 is highly produced by human cancer cells and elevated FGL1 in the plasma of cancer patients is associated with a poor prognosis and resistance to anti-PD-1/B7-H1 therapy. Our findings reveal an immune evasion mechanism and have implications for the design of cancer immunotherapy. In Brief FGL1 is identified as a major ligand for the inhibitory receptor LAG3 and its blockade can potentiate anti-tumor T cell responses