LILRA1, also known as CD85i and LIR-6, is an approximately 70 kDa variably glycosylated transmembrane protein that regulates immune cell activation. Mature human LILRA1 consists of a 445 amino acid (aa) extracellular domain (ECD) with 4 Ig-like domains, a 21 aa transmembrane segment, and a 7 aa cytoplasmic tail. LILRA1 may act as receptor for class I MHC antigens.