Identification and characterization of the rat homologue of LAIR-1

Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is a cell-surface molecule that functions as an inhibitory receptor on various immune cells in both humans and mice. We have cloned a LAIR-1 homologue from the rat that we have named rat LAIR-1. The LAIR-1 gene maps to rat chromosome 1q12 in a region showing conserved synteny with human chromosome 19q13.4 and mouse chromosome 7, where the leukocyte receptor cluster is located. Rat LAIR-1 shows 40 and 71% protein sequence identity with human LAIR-1 and mouse LAIR-1, respectively, has a single Ig-like domain and contains two immunoreceptor tyrosine-based inhibitory motif-like sequences in its cytoplasmic tail. Soluble rat LAIR-1 fusion proteins bind to the same adherent cell lines as human LAIR-1 and mouse LAIR-1, indicating that a putative ligand for all the LAIR-1 molecules is expressed on these cells. Furthermore, we show that rat and mouse LAIR-1 bind the same molecule expressed on human HT29 cells. Since many autoimmune diseases are studied in rat models, identification of rat LAIR-1 allows for in vivo studies on the function of LAIR molecules in these systems.