The leukocyte immunoglobulin-like receptors (LILR) comprise a family of activating and inhibitory type immunoreceptors whose genes are located in the same locus that encodes killer cell Ig-like receptors (KIRs) (1). Human LILRA5, also known as ILT11, LIR-9, and CD85f, consists of a 227 amino acid (aa) extracellular domain (ECD), a 21 aa transmembrane segment, and a 10 aa cytoplasmic tail (2). The ECD contains two Ig-like domains (3), and the transmembrane segment contains a positively charged aspartic acid residue which may mediate its association with the signaling molecule, FcR common gamma chain (4). Alternative splicing generates additional isoforms with a 12 aa deletion within the signal peptide and/or a 27 aa substitution for the C-terminal 61 residues. This substitution encompasses both the transmembrane and cytoplasmic regions. LILRA5 is expressed by monocytes, macrophages, and neutrophils (2, 4). It is found as an approximately 40 kDa molecule on the cell surface, while a soluble 25 kDa form can be released into the synovial fluid of rheumatoid arthritis patients (2, 4). Cross-linking of LILRA5 on monocytes induces the expression of pro-inflammatory cytokines (IL-1 beta, IL-6, TNF-alpha) as well as the anti-inflammatory IL-10 (2, 4). R&D Systems in-house testing indicates that LILRA5 binds to Angiopoietin-like 7, consistent with the demonstrated functional interactions between other members of these protein families (5).