>95%, by SDS-PAGE visualized with Silver Staining and quantitative densitometry by Coomassie® Blue Staining.
<0.10 EU per 1 μg of the protein by the LAL method.
Measured by its binding ability in a functional ELISA. When Recombinant Human IgA
is immobilized at 5 μg/mL, 100 μL/well, the concentration of Recombinant Cynomolgus Monkey FCAR/CD89
that produces 50% of the optimal binding
response is 0.5-2.5 μg/mL.
Mouse myeloma cell line, NS0-derived Gln22-Asn227, with a C-terminal 6-His tag
When Human IgA iscoated at 5 µg/mL (100 μL/well), Recombinant Cynomolgus MonkeyFCAR/CD89 (Catalog # 9516-FA) binds with an ED50 of 0.5-2.5 μg/mL.
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)
Wines, B. D. and P. M. Hogarth (2006) Tissue Antigens 68:103.
Otten, M. A. and M. van Egmon (2004) Immunol. Lett. 92:23.
Montiero, R. C. and J. G. J. van de Winkel (2003) Annu. Rev. Immunol. 21:177.
Maliszewski, C. R. et al. (1990) J. Exp. Med. 172:1665.
Launay, P. et al. (1999) J. Biol. Chem. 274:7216.
Pasquier, B. et al. (2005) Immunity 22:31.
Shen, L. et al. (2001) Blood 97:205.
Herr, Y. et al. (2003) Nature 423:614.
Patry, C. et al. (1996) J. Immunol. 156:4442.
Togo, S. et al. (2003) FEBS Lett. 535:205.
van der Boog, P. J. M. et al. (2002) J. Immunol. 168:1252.
Hamre, R. et al. (2003) Scand. J. Immunol. 57:506.
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