CD21 Mouse mAb: FAQs for Research Use

CD21 Mouse mAb is a mouse-derived monoclonal antibody targeting the CD21 antigen (Complement Receptor 2, CR2), widely used in immunology research to identify and characterize B lymphocyte populations and study complement-mediated immune responses.

Product Name

CD21 Mouse mAb

SKU / Catalog Number

Ab348616

Host Species

Mouse

Antibody Type

Monoclonal Antibody (mAb)

Target Antigen

CD21 (Complement Receptor 2, CR2)

Reference Clone

absea#KC-2416

What Is CD21 and Why Is It Important?

CD21, also known as Complement Receptor 2 (CR2) and encoded by the CR2 gene, is a cell-surface glycoprotein predominantly expressed on mature B lymphocytes, follicular dendritic cells, and a subset of T lymphocytes. It binds complement fragments iC3b, C3d, and C3dg, as well as the Epstein–Barr virus (EBV) glycoprotein gp350, making it a critical node in both innate and adaptive immunity.

In B cells, CD21 forms the B cell co-receptor complex together with CD19 and CD81 (TAPA-1). Coligation of CD21 with the B cell receptor (BCR) lowers the threshold for B cell activation by several orders of magnitude, amplifying humoral immune responses. CD21 is therefore a key marker for identifying mature naïve B cells, germinal centre B cells, and marginal zone B cells in lymphoid tissues.

Typical Applications of CD21 Mouse mAb

CD21 Mouse mAb (Ab348616) is suitable for several standard immunological and cell biology techniques. Common applications include:

• Flow Cytometry (FC): Immunophenotyping of B lymphocyte subsets from peripheral blood, spleen, lymph nodes, and bone marrow. CD21 expression level helps distinguish follicular B cells (CD21^int) from marginal zone B cells (CD21^hi) and transitional B cells (CD21^lo).
• Immunohistochemistry (IHC): Detection of CD21-positive B cells and follicular dendritic cell networks in formalin-fixed, paraffin-embedded (FFPE) tissue sections of lymphoid organs.
• Immunofluorescence (IF): Visualisation of CD21 distribution on cell surfaces and in tissue sections.
• Western Blot (WB): Detection of CD21 protein under denaturing conditions, subject to antibody clone performance under reducing conditions.

Please consult the specific datasheet for Ab348616 to confirm validated application details and recommended dilutions before use.

Storage, Handling, and Stability

Proper storage and handling of monoclonal antibodies are essential to maintain their activity and specificity over time. General best-practice guidelines for CD21 Mouse mAb include:

• Short-term storage (up to 1 month): Store at 4 °C in the dark.
• Long-term storage: Aliquot into single-use volumes and store at −20 °C or −80 °C to avoid repeated freeze–thaw cycles, which degrade antibody performance.
• Buffer: The antibody is typically supplied in PBS containing a carrier protein (e.g., BSA or glycerol) and a preservative such as sodium azide. Do not use sodium-azide-containing preparations in cell culture or with HRP-conjugated secondary antibodies.
• Handling: Keep on ice during experiments; centrifuge briefly before opening to consolidate contents.

Refer to the Certificate of Analysis (CoA) and product datasheet for Ab348616 for the exact formulation, concentration, and expiry information specific to your lot.

Troubleshooting Common Issues

If you experience suboptimal results with CD21 Mouse mAb, consider the following troubleshooting steps:

• High background: Increase blocking stringency (e.g., 5% normal serum from the secondary antibody host species). Optimise antibody dilution. Ensure thorough washing steps.
• No or weak signal: Verify that your target cell type or tissue expresses CD21. Check antibody lot viability; avoid antibody that has experienced freeze–thaw degradation. Confirm that the secondary antibody is appropriate for a mouse primary antibody. For IHC, validate antigen retrieval method (heat-induced vs. enzymatic).
• Non-specific bands (WB): CD21 is a large glycoprotein; molecular weight may appear higher than predicted due to glycosylation. Use appropriate positive controls (e.g., Raji or Ramos B cell lysates).
• Flow cytometry aggregates: Filter samples through a 35–40 µm cell strainer before acquisition; include a viability dye to gate on live cells only.

Contact Aladdin Scientific technical support for application-specific guidance if issues persist.

Ordering and Regulatory Information

CD21 Mouse mAb is available from Aladdin Scientific under catalog number Ab348616. This product is intended for research use only (RUO) and is not approved for diagnostic or therapeutic use in humans or animals.

To order, visit the Aladdin Scientific website, search by catalog number Ab348616, or contact your regional sales representative. Bulk quantities and custom conjugation inquiries can be directed to our sales team. Please review the Safety Data Sheet (SDS) prior to handling and ensure compliance with your institution's biosafety regulations regarding the use of animal-derived biological reagents.

Frequently asked questions

What species does CD21 Mouse mAb (Ab348616) react with?

The species reactivity of Ab348616 should be confirmed in the official product datasheet, as it depends on the specific clone (absea#KC-2416). Mouse monoclonal antibodies targeting CD21 typically show reactivity against human CD21, but cross-reactivity with mouse, rat, or other species must be verified per lot. Please download the current datasheet from the Aladdin Scientific product page for confirmed reactivity data.

What is the recommended dilution for CD21 Mouse mAb in flow cytometry?

Optimal dilution varies by application, instrument, and sample type and must be determined empirically. As a general starting point for flow cytometry, many CD21 monoclonal antibodies are used at 1–5 µg per 10⁶ cells in a 100 µL reaction volume; however, the specific recommended dilution for Ab348616 is stated in its product datasheet. Always titrate the antibody to determine the optimal concentration for your experimental conditions.

Can CD21 Mouse mAb be used for immunohistochemistry on FFPE tissue sections?

CD21 antibodies are commonly used in IHC to stain B cell follicles and follicular dendritic cell networks in lymphoid tissue FFPE sections. Antigen retrieval is typically required; heat-induced epitope retrieval (HIER) using citrate buffer (pH 6.0) or EDTA buffer (pH 9.0) is commonly employed. Please verify that IHC is a validated application for Ab348616 by consulting its datasheet, and perform optimisation experiments to determine the best retrieval method and antibody dilution for your tissue type.

How should I store CD21 Mouse mAb to maximise shelf life?

For optimal shelf life, aliquot the antibody into single-use volumes immediately upon receipt to avoid repeated freeze–thaw cycles, and store at −20 °C for long-term preservation. Short-term storage (up to one month) at 4 °C in the dark is acceptable. Avoid exposure to light and temperature fluctuations. Always refer to the specific storage instructions on the Ab348616 product label and datasheet, as formulation details may affect recommended conditions.

Is CD21 Mouse mAb (Ab348616) suitable for use as a research-only reagent or can it be used in clinical diagnostics?

Ab348616 is strictly a Research Use Only (RUO) reagent and has not been validated, cleared, or approved for in vitro diagnostic (IVD) use or any clinical application. It must not be used in clinical laboratories for diagnostic purposes without appropriate regulatory authorisation. Researchers should ensure compliance with all relevant institutional and national regulations governing the use of biological reagents.

References

1. Fearon DT, Carroll MC. Regulation of B lymphocyte responses to foreign and self-antigens by the CD19/CD21 complex. Annual Review of Immunology. 2000;18:393–422.
2. Tedder TF, Inaoki M, Sato S. The CD19-CD21 complex regulates signal transduction thresholds governing humoral immunity and autoimmunity. Immunity. 1997;6(2):107–118.
3. Aladdin Scientific. Ab348616 – CD21 Mouse mAb product datasheet. Accessed via Aladdin Scientific official website.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.