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Biotin Anti-Human CD21 Antibody

Cat # Size Price Quantity
10890325 ug$70
108904100 ug$180

  Bulk/Custom

Product Details

CloneTHB5
ApplicationFlow Cytometry
ReactivityHuman
FormatBiotin
Target NameCD21, Complement C3d receptor (C3dR), complement receptor 2 (CR2), Epstein-Barr virus receptor
IsotypeMouse IgG2a
Antibody TypeMonoclonal
Regulatory StatusRUO
FormulationPhosphate-buffered solution, pH 7.2, containing 0.09% sodium azide and 0.2% (w/v) BSA
Protein Concentration0.2 mg/mL
Storage and HandlingThe antibody solution should be stored undiluted between 2°C and 8°C, and protected from prolonged exposure to light. Do not freeze.
Recommended UsageFor flow cytometric staining, it is recommended to use less than 0.1 µg of this reagent per 0.5-1.0 million cells in a 100 µL volume. Optimal reagent performance should be determined by titration for each specific application. For detection, use a secondary reagent with this product.
RRIDAB_3738867
Research AreasB cells, follicular Dendritic cells, EBV, Infectious Diseases
See All FormatsClone THB5

Background Information

CD21, also known as complement receptor 2 (CR2), is a surface glycoprotein expressed primarily on mature B cells, follicular dendritic cells, and certain epithelial cells. It serves as a receptor for complement fragments and viral particles, playing a central role in regulating adaptive immune responses. CD21 is essential for the activation and maturation of B cells, helping to lower the threshold for B cell receptor (BCR) signaling by binding complement-tagged antigens, thereby enhancing antibody production and immune memory formation.

Structurally, CD21 is a type I transmembrane protein of approximately 145 kDa and belongs to the regulators of complement activation (RCA) family. It comprises 15 or 16 extracellular short consensus repeats (SCRs), each containing about 60 amino acid residues stabilized by disulfide bonds. These SCR domains contribute to ligand recognition and binding, while the short cytoplasmic tail participates in intracellular signaling through interactions with other surface molecules, such as CD19 and CD81, forming the B cell co-receptor complex. This multimolecular complex plays a critical role in amplifying B cell activation in response to antigen engagement.

The principal ligands for CD21 are complement fragments C3d, iC3b, and C3dg, which are generated during complement activation. CD21 also acts as a receptor for the Epstein-Barr virus (EBV) glycoprotein gp350/220, facilitating viral entry into B cells and establishing latent infection. This dual function - immune modulation and viral susceptibility - underpins its significance in both health and disease.

CD21 involvement in disease extends beyond viral infection. Dysregulation of CD21 expression or signaling contributes to immune-related disorders such as systemic lupus erythematosus (SLE), where altered receptor levels impair clearance of immune complexes and promote autoreactivity. In chronic lymphocytic leukemia (CLL) and some lymphomas, CD21 expression serves as a diagnostic and phenotypic marker for subtyping B cell malignancies. Conversely, its engagement by EBV plays a role in the development of EBV-associated cancers such as Burkitt lymphoma and nasopharyngeal carcinoma.

Therapeutically, CD21 offers potential as a target for modulating immune function and managing infection or autoimmunity. Inhibition of CD21-Epstein-Barr virus interactions represents a strategy for preventing viral infection, while modulation of the CD21-C3d pathway may fine-tune B cell responses in autoimmune and vaccine contexts. Ongoing studies continue to define how manipulating CD21 signaling could optimize immunotherapy and immune tolerance.

Isotype Control

Biotin Mouse IgG2a Isotype Control Antibody

Data Sheets

Biotin Anti-Human CD21 Antibody TDS

Related Protocols

Flow Cytometry Protocol

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Biotin Anti-Human CD19 Antibody, Clone 019AM2b

iF405 Anti-Human CD81 Antibody, Clone 5A6

PE Anti-Human CD81 Antibody, Clone 5A6

Frequently Asked Questions

How do I determine the optimal antibody concentration/titer for my experiment?
We recommend titrating each new antibody lot on your own cell type and instrument, since optimal concentration depends on cell density, target expression level, and cytometer sensitivity. Suggested starting dilutions or test sizes (e.g., µg or µl per 10^6 cells) are provided on the product page as a starting reference point, not a fixed requirement.
Can these antibodies be used for intracellular or intranuclear staining, or only surface staining?
Intended use (surface, intracellular, or both) is specified per product, indicated under Application. The appropriate Related Protocol is linked for each product. If you need to detect both surface and intracellular markers in the same panel, confirm each antibody's compatibility with your fixation/permeabilization protocol before combining them.
What controls should I use alongside these antibodies?
Matched isotype controls (same host species, isotype, and conjugate) are available for most clones to help distinguish specific binding from background/non-specific staining and are linked on each product page. Unstained, single-color compensation, and fluorescence-minus-one (FMO) controls are also recommended, especially for multicolor panel design.
Can I combine InnoCyto Flow Cytometry antibodies into a multicolor panel?
Yes — antibodies across our catalog are designed to be panel-compatible, and conjugate options are offered specifically to support multiplexing. When building a panel, pair bright fluorophores with low-expression targets, avoid excessive spectral overlap, and confirm compensation is set up correctly for your specific fluorochrome combination. Use our Panel Builder to simplify the process.

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