Recombinant Mouse PILR-beta Protein, CF

PILR-beta (paired immunoglobulin-like type 2 receptor-beta) is one of two members of a small family of immunoregulatory Ig-superfamily receptors (1, 2). It is a counterpart to PILR-alpha and it likely arose through PILR-alpha gene duplication and rearrangement (1). The PILRs represent one of many pairs of Ig-like domain-containing receptors that participate in immune regulation. PILR-beta and -alpha should not be confused with the similarly named PIRs (also paired immunoglobulin-like receptors), or the functionally-related SIRP and ILT/LILR/CD85/LIR family of receptors (2). While PIRs, ILTs and SIRPs contain three to six Ig-like domains in their extracellular region, PILR-beta and -alpha show only one Ig-like region in their extracellular domain (ECD) (1, 2). Mouse PILR-beta is a 196 amino acid (aa) type I transmembrane (TM) protein (3). It contains a 167 aa ECD, a 21 aa TM segment, and a short 8 aa cytoplasmic region. The ECD shows a V-type Ig-like domain (aa 39 - 135), while the TM segment contains a positively-charged Lys at position # 202. This Lys is known to interact with the transmembrane signaling adaptor protein DAP12, making PILR-beta an activating receptor. Activation of PILR-beta through CD99 ligation induces NK cell cytotoxicity and dendritic cell secretion of NO and TNF-alpha (3). Mouse PILR-beta is found on NK cells, neutrophils, macrophages, and monocyte-derived dendritic cells (3). Mouse PILR-beta ECD is 44% and 75% aa identical to human and rat PILR-beta ECD, respectively; it is 75% aa identical to the ECD of mouse PILR-alpha (3). Evidence suggests that mouse PILR-beta will not be active in a human system (3). Potential isoforms of PILR-beta have been reported. One shows an alternate start site at Met14, a second shows a 21 aa substitution for the C-terminal 67 aa, and a third exhibits multiple polymorphisms for an overall aa identity of 86% (4, 5, 6).