Source: HEK 293 cell-derived.Recombinant PDL1-FLAG protein is human PDL1 (amino acids 19-239) fused with the FLAG tag at the C-terminus.Purity: >95% by SDS-PAGE under reducing conditions.Formulation: 0.2 μM filtered solution of 50 mM Tris, 150 mM NaCl, pH 7.5.Endotoxin Level: Less than 1 EU/ug of protein as determined by LAL method.Shipping: The product is shipped with ice pack. Upon receipt, store it immediately at the temperature recommended below.Stability & Storage: Use a manual defrost freezer and avoid repeated freeze-thaw cycles.1 month from date of receipt, 2 to 8°C as supplied.3 months from date of receipt, -20°C to -70°C as supplied. Background Programmed Death Ligand 1 (PDL1) is a member of the growing B7 family of immune proteins that provide signals for both stimulating and inhibiting T cell activation. It is a 40kDa type 1 transmembrane protein that has been speculated to play a major role in suppressing the immune system during particular events such as pregnancy, tissue allografts, autoimmune disease and other disease states such as hepatitis. PD-L1 binds to its receptor, PD-1, found on activated T cells, B cells, and myeloid cells, to modulate activation or inhibition.