Recombinant Cynomolgus Monkey FCAR/CD89 Protein, CF

Recombinant Cynomolgus Monkey FCAR/CD89 Protein, CF Summary

Product Specifications

Product Datasheets

Carrier Free

CF stands for Carrier Free (CF). We typically add Bovine Serum Albumin (BSA) as a carrier protein to our recombinant proteins. Adding a carrier protein enhances protein stability, increases shelf-life, and allows the recombinant protein to be stored at a more dilute concentration. The carrier free version does not contain BSA.

In general, we advise purchasing the recombinant protein with BSA for use in cell or tissue culture, or as an ELISA standard. In contrast, the carrier free protein is recommended for applications, in which the presence of BSA could interfere.

Background: FCAR/CD89

FCAR, also called Fc alpha RI or CD89, is a variably glycosylated 50-100 kDa myeloid-specific type I transmembrane (TM) Fc receptor for IgA and is a member of the multi-chain immune recognition receptor (MIRR) family (1-3). Cynomolgus FCAR is predicted to contain a 21 amino acid (aa) signal sequence and 206 aa extracellular (ECD), 19 aa TM and 41 aa cytoplasmic domains (4). The Arg230 within the TM domain of human FCAR supports interaction with the ITAM-containing signaling subunit, FcR gamma, which contains a TM Asp (5-7). Two ECD C2-type Ig-like domains (EC1 and 2) are oriented at right angles (8). Up to two molecules of FCAR can bind one molecule of serum IgA via EC1 (8). Many human FCAR splice variants have been reported, but only two have been identified as proteins (9, 10). The a.2 form, which lacks 22 aa just prior to the TM domain, is exclusively expressed in alveolar macrophages. The a.3 form lacks EC2. FCAR binds monomeric, polymeric and secretory IgA, but does not mediate the barrier function of secretory IgA in mucosal epithelium (1-3). Shedding and circulation of polymeric IgA/FCAR immune complexes has been reported (11). Circulating neutrophils, eosinophils, and monocytes express FCAR (12). Tissue expression of FCAR is mainly from neutrophils; FCAR is down-regulated as monocytes differentiate to tissue macrophages (12). On neutrophils, a significant amount of FCAR lacks FcR gamma, but can still be endocytosed to early endosomes and recycled to the cell surface (5). Binding of serum IgA to FCAR is transient and anti-inflammatory, inhibiting IgG or IgE-induced degranulation (6). Sustained aggregation of FCAR results in inflammatory responses (6). FcR gamma signaling is required for these and for transport to late endosomes (5-7). Within ECD, Cynomolgus FCAR shows 83% aa identity with human FCAR. No ortholog occurs in mouse. FCAR structure resembles the KIR/ILT/LIR/MIR family more than other IgA receptors, including pIgR, Fc alpha /μR, asialoglycoprotein receptor (ASGR1) and transferrin receptor (TfR) (1-3).

Related Research Areas

• Fc Receptors
• ITIM/ITAM Immunoreceptors and Related Molecules
• Monocyte Markers