LAG3 (lymphocyte activation gene 3) is an inhibitory CD4 (cluster of differentiation)-related molecule, and is expressed by activated CD4⁺ and CD8⁺ T cells.

LAG3 (lymphocyte activation gene 3) is a negative regulator of T-cell proliferation where it suppresses T-cell receptor (TCR)-mediated calcium fluxes and modulates the memory T-cell pool size. It is a CD4 (cluster of differentiation) homolog that functions as a ligand for MHC (major histocompatibility complex) II. Membrane expression of LAG3 modulates the suppressive function of Tregs (T-regulatory) both in vivo and in vitro. HIV-1 (human immunodeficiency virus) infection results in significant increase in LAG3 peripheral blood and lymph node expression, which is exhibited on both CD4⁺ and CD8⁺ T cells, and this is linked with disease progression. In melanoma, this protein is responsible for TLR (Toll-like receptor)-independent activation of plasmacytoid dendritic cells (pDCs) at tumor sites, which is partially implicated in driving an immune-suppressive environment.

Solution in PBS.

The sequence coding for the 4 extracellular Ig-like domains of human LAG-3 (D1-D4) is fused to the Fc portion of human IgG1.