Name: APC Human CD33 Protein (C-Fc)
Brand: InnoCyto
SKU: 809703
Price: 245 USD
Availability: InStock

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APC Human CD33 Protein (C-Fc)

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Cat #	Size	Price	Quantity
809703	25 ug	$245
809704	100 ug	$595

Bulk/Custom

Product Details

Application	Flow Cytometry
Format	Liquid, APC
Expression Host	CHO
Target Name	CD33, SIGLEC3, gp67
Species	Human
Sources	Recombinant Human CD33 Protein (Asp18-His259) with C-terminus Fc-tag is expressed in CHO cell and conjugated to APC.
Accession Number	P20138
Molecular Weight	The protein has a predicted molecular weight of 53 kDa. Under DTT-reducing conditions, it migrates at approximately 70-90 kDa on SDS-PAGE prior to conjugation.
Affinity Tag	C-Fc
Regulatory Status	RUO
Formulation	1xPBS buffer, pH7.4, 0.09% NaN3 with a carrier protein
Endotoxin level	Not tested
Protein Concentration	25µg size is bottled at 0.1mg/mL concentration. 100 µg size is bottled at lot specific concentration.
Storage and Handling	Briefly centrifuge the vial upon receipt. An unopened vial may be stored at 2–8°C for up to six months.
Research Areas	Monocytes, Macrophages, Dendritic cells, Innate Immunity, Cancer Marker

Background Information

CD33, also known as Siglec-3 (sialic acid-binding immunoglobulin-like lectin 3), is a transmembrane receptor belonging to the Siglec family of proteins that plays an important role in regulating immune cell function. CD33 is predominantly expressed on myeloid lineage cells, including monocytes, macrophages, granulocytes, and myeloid dendritic cells, as well as on myeloid progenitor cells in the bone marrow. The protein functions as an inhibitory receptor that modulates immune responses by dampening cellular activation signals. Upon ligand binding, CD33 recruits phosphatases that suppress inflammatory signaling pathways, thereby maintaining immune homeostasis and preventing excessive immune activation.

Structurally, CD33 is a type I transmembrane glycoprotein of approximately 67 kDa consisting of an extracellular region with two immunoglobulin-like domains (one V-set and one C2-set domain), a single transmembrane domain, and a cytoplasmic tail containing immunoreceptor tyrosine-based inhibitory motifs (ITIMs). The V-set domain at the N-terminus contains the sialic acid-binding site responsible for ligand recognition. The cytoplasmic ITIMs, when phosphorylated, recruit SHP-1 and SHP-2 phosphatases that deliver inhibitory signals to suppress cell activation, proliferation, and cytokine production. This structural organization enables CD33 to function as a checkpoint receptor that fine-tunes myeloid cell responses.

CD33 binds to sialylated glycans, particularly α2,6-linked and α2,3-linked sialic acids, which are present on glycoproteins and glycolipids on cell surfaces and in the extracellular matrix. These sialic acid-containing ligands are widely distributed throughout the body, allowing CD33 to recognize "self" markers and maintain immune tolerance. The protein's ability to recognize sialylated structures makes it an important regulator of innate immunity and inflammation.

In disease contexts, CD33 is highly significant in acute myeloid leukemia (AML), where it is expressed on leukemic blasts in approximately 85-90% of cases. This expression pattern has made CD33 an attractive therapeutic target. Gemtuzumab ozogamicin, an antibody-drug conjugate targeting CD33, was the first CD33-directed therapy approved for AML treatment, delivering a cytotoxic payload specifically to CD33-positive leukemic cells. Additionally, CD33 genetic variants have been associated with Alzheimer's disease risk, as the protein is expressed on microglia and may influence neuroinflammation and amyloid-beta clearance. Beyond gemtuzumab ozogamicin, newer CD33-targeted therapies under development include bispecific antibodies, CAR-T cells, and next-generation antibody-drug conjugates, establishing CD33 as a key target in hematologic malignancy treatment and potentially in neurodegenerative disease modulation.

Frequently Asked Questions

How is a fluorescence labeled recombinant protein different from a labeled antibody for the same target?

A labeled protein (e.g., a fluorescent ligand or receptor domain) binds its natural counter-receptor or binding partner directly, making it useful for functional binding assays, competition/blocking studies, and receptor occupancy measurements — whereas an antibody typically binds a specific epitope regardless of the protein's natural binding activity. Choose the labeled protein format when you need to assess biologically relevant binding interactions rather than simple target detection.

Can these proteins be used in flow cytometry, and are they compatible with other panel reagents?

Yes, fluorescence labeled proteins are commonly used in flow cytometry panels to detect receptor expression or ligand binding on live cells, and are designed to be compatible with standard antibody panels. As with any multicolor panel, confirm spectral compatibility and run proper compensation controls when combining labeled proteins with labeled antibodies.

What controls should I use with fluorescence labeled recombinant proteins?

Recommended controls include an unlabeled/unconjugated version of the same protein (for competition/blocking controls), an irrelevant labeled protein of the same conjugate as a background control, and standard unstained/FMO controls for gating. Species- or format-matched controls are noted on the product page where available.

What applications are these proteins validated for?

Common applications include receptor binding assays, flow cytometry-based ligand-receptor studies, ELISA-based detection, and blocking/competition assays to study receptor occupancy or antagonist activity. Specific validated applications and recommended usage concentrations vary by product and are detailed on the individual product page.

Have a product or application question? Consult our FAQs or contact us.

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