LAG-3

Lymphocyte-activation gene 3 (LAG-3) is an immune checkpoint receptor that is expressed on the surface of both cytotoxic T cells and regulatory T cells (Tregs) and functions to control T cell response, activation and growth.^1,2 LAG-3 expression is being evaluated as a biomarker to predict response to treatment.³

In certain situations where T cells experience prolonged exposure to an antigen, such as cancer or chronic infection, the T cells become desensitized and lose their ability to activate and multiply in the presence of the antigen. The desensitized T cells will also progressively fail to produce cytokines (proteins that assist in the immune response) and kill the target cells. This process is called T cell exhaustion and is associated with an increased expression of inhibitory receptors, such as LAG-3.⁴ 

References
1. Huang CT et al. Immunity. 2004; 21:503-513.
2. Baixeras E et al. J Exp Med. 1992; 176:327-337.
3. Ascierto PA et al. J Clin Oncol. 2017. 35(15):9520-9520.
4. Wherry, E. J. Nature Immunol. 12, 492–499 (2011).