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PE Human CD19 Protein (C-Fc)

CHO cells transfected with either CD19 CAR or Mock plasmid were stained with PE conjugated CD19 (C-Fc) protein at 1ug_test

Cat #	Size	Price	Quantity
807401	25 ug	$245
807402	100 ug	$595

Bulk/Custom

Product Details

Application	Flow Cytometry
Format	Liquid, PE
Expression Host	CHO
Target Name	CD19, B4, CVID3
Species	Human
Sources	Recombinant Human CD19 Protein (Glu21-Lys291) with C-terminus Fc-tag is expressed in CHO cell and conjugated to PE.
Accession Number	P15391
Molecular Weight	The protein has a predicted molecular weight of 56.2 kDa. Under DTT-reducing conditions, it migrates at approximately 70-80 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	B cells, Plasma cells, Cancer Marker, follicular Dendritic cells

Background Information

CD19 is a B cell-specific transmembrane glycoprotein that serves as a central regulator of B cell activation, signaling, and development. It is expressed throughout most stages of B cell differentiation, from early pro-B cells through mature peripheral B cells, but is lost upon terminal differentiation into plasma cells. Because of its broad and consistent expression on B lineage cells, CD19 is widely used as a defining marker of the B cell compartment.

Structurally, CD19 is a type I transmembrane protein with two extracellular immunoglobulin-like domains, a single transmembrane region, and a long cytoplasmic tail. The intracellular domain contains multiple tyrosine residues that become phosphorylated following B cell receptor (BCR) engagement. CD19 functions as part of a larger co-receptor complex that includes CD21 (complement receptor 2), CD81 (TAPA-1), and CD225, which together modulate BCR signaling strength and sensitivity.

Functionally, CD19 acts as a signaling amplifier for the BCR. When antigen binds the BCR, CD19 is rapidly phosphorylated by Src family kinases, creating docking sites for signaling molecules such as PI3K. This lowers the threshold for B cell activation, enhances proliferation, promotes survival, and supports antibody production. Through this role, CD19 helps shape humoral immune responses and ensures efficient activation of B cells in response to antigen, particularly when antigen is present at low concentrations. Unlike many immune receptors, CD19 does not have a well-defined classical ligand. Instead, its activity is regulated through its association with the BCR complex and co-receptors. The CD19-CD21 interaction is functionally linked to recognition of complement-tagged antigens, indirectly coupling innate and adaptive immune signals to enhance B cell responses.

Dysregulation of CD19 signaling contributes to disease. Overactive CD19-mediated signaling has been associated with autoimmune diseases such as systemic lupus erythematosus, where hyperresponsive B cells drive autoantibody production. CD19 is also expressed on the vast majority of B cell malignancies, including B cell acute lymphoblastic leukemia (B-ALL), chronic lymphocytic leukemia, and many non-Hodgkin lymphomas, making it a critical diagnostic and therapeutic target.

In therapeutics, CD19 is one of the most successful targets in modern immuno-oncology. CD19-directed therapies include monoclonal antibodies, antibody–drug conjugates, bispecific T cell engagers, and chimeric antigen receptor (CAR) T cell therapies, many of which have produced durable remissions in refractory B cell cancers. Beyond cancer, CD19-targeted strategies are being explored to selectively deplete pathogenic B cells in autoimmune disease, underscoring CD19’s central role in both disease biology and therapeutic innovation.

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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