Fc fragment of IgA receptor (FCAR) is a human gene[3] that codes for the transmembrane receptor FcαRI, also known as CD89 (Cluster of Differentiation 89). FcαRI binds the heavy-chain constant region of Immunoglobulin A (IgA) antibodies. FcαRI is present on the cell surface of myeloid lineage cells, including neutrophils, monocytes, macrophages, and eosinophils, though it is notably absent from intestinal macrophages and does not appear on mast cells. FcαRI plays a role in both pro- and anti-inflammatory responses depending on the state of IgA bound. Inside-out signaling primes FcαRI in order for it to bind its ligand, while outside-in signaling caused by ligand binding depends on FcαRI association with the Fc receptor gamma chain (FcR γ-chain). Though FcαRI is part of the Fc receptor immunoglobulin superfamily, the protein's primary structure is similar to receptors in the leukocyte receptor cluster (LRC), and the FCAR gene appears amidst LRC genes on chromosome 19. This contrasts with the location of other members of the Fc receptor immunoglobulin superfamily, which are encoded on chromosome 1. Additionally, though there are equivalents to FCAR in several species, there is no such homolog in mice.
Background References
1. Cambier A et al. Soluble CD89 is a critical factor for mesangial proliferation in childhood IgA nephropathy. Kidney Int. 2022 Feb
2. van Delft MAM et al. Antagonizing FcalphaR1 (CD89) as treatment in IgA-mediated chronic inflammation and autoimmunity. Front Immunol. 2023 Apr
Western blot analysis of CD89 on different lysates with Rabbit anti-CD89 antibody (HA722549) at 1/1,000 dilution.
Lane 1: HL-60 cell lysate (20 µg/Lane) Lane 2: Raji cell lysate (20 µg/Lane) Lane 3: A549 cell lysate (20 µg/Lane) Lane 4: U-87 MG cell lysate (20 µg/Lane) Lane 5: Jurkat cell lysate (20 µg/Lane) Lane 6: Human lung tissue lysate (40 µg/Lane)
Predicted band size: 32 kDa Observed band size: 75 kDa
Exposure time: 10 seconds; ECL: K1801;
4-20% SDS-PAGE gel.
Proteins were transferred to a PVDF membrane and blocked with 5% NFDM/TBST for 1 hour at room temperature. The primary antibody (HA722549) at 1/1,000 dilution was used in 5% NFDM/TBST at 4℃ overnight. Goat Anti-Rabbit IgG - HRP Secondary Antibody (HA1001) at 1/50,000 dilution was used for 1 hour at room temperature.
Immunocytochemistry analysis of HL-60 cells labeling CD89 with Rabbit anti-CD89 antibody (HA722549) at 1/100 dilution.
Cells were fixed in 4% paraformaldehyde for 20 minutes at room temperature, permeabilized with 0.1% Triton X-100 in PBS for 5 minutes at room temperature, then blocked with 1% BSA in 10% negative goat serum for 1 hour at room temperature. Cells were then incubated with Rabbit anti-CD89 antibody (HA722549) at 1/100 dilution in 1% BSA in PBST overnight at 4 ℃. Goat Anti-Rabbit IgG H&L (iFluor™ 488, HA1121) was used as the secondary antibody at 1/1,000 dilution. PBS instead of the primary antibody was used as the secondary antibody only control. Nuclear DNA was labelled in blue with DAPI.
Beta tubulin (M1305-2, red) was stained at 1/100 dilution overnight at +4℃. Goat Anti-Mouse IgG H&L (iFluor™ 594, HA1126) was used as the secondary antibody at 1/1,000 dilution.
Please note: All products are "FOR RESEARCH USE ONLY AND ARE NOT INTENDED FOR DIAGNOSTIC OR THERAPEUTIC USE"