Recombinant Human LAG-3/CD223 Protein (C-His)

Measured by functional ELISA. Immobilized recombinant human LAG-3 binds recombinant human MHC class II and the LAG-3 ligand FGL1 with EC50 values in the low-ng/mL range; binding is blocked by reference anti-LAG-3 antibodies.

LAG-3 (lymphocyte-activation gene 3, CD223) is an inhibitory receptor structurally related to CD4 that has emerged as the most clinically advanced checkpoint target beyond the PD-1/CTLA-4 axis. Expressed on activated T cells, Tregs, NK cells and B cells, LAG-3 binds MHC class II molecules with far higher affinity than CD4 and additionally engages the liver-expressed ligand FGL1; through its cytoplasmic KIEELE motif it dampens T cell proliferation and cytokine output. LAG-3 is co-expressed with PD-1 on exhausted tumor-infiltrating lymphocytes, and the fixed-dose combination of nivolumab with the anti-LAG-3 antibody relatlimab (Opdualag) established LAG-3 blockade as a validated cancer therapy. The four extracellular Ig-like domains, including the stabilizing D2–D2 dimer, make recombinant LAG-3 an essential reagent for bispecific screening, ligand-blocking assays and combination-immunotherapy development.