CD21 Antibody [Unconjugated]

Daudi human Burkitt's lymphoma cell line was stained with Sheep Anti-Human CD21 Antigen Affinity‑purified Polyclonal Antibody (Catalog # AF4909, filled histogram) or control antibody (Catalog # 5‑001‑A, open histogram), followed by NorthernLights™ 557-conjugated Anti-Sheep IgG Secondary Antibody (Catalog # NL010).

CD21 was detected in immersion fixed paraffin-embedded sections of Human Tonsil using Sheep Anti-Human CD21 Antigen Affinity-purified Polyclonal Antibody (Catalog # AF4909) at 3 µg/mL for 1 hour at room temperature followed by incubation with the Anti-Sheep IgG VisUCyte™ HRP Polymer Antibody (Catalog # VC006). Before incubation with the primary antibody, tissue was subjected to heat-induced epitope retrieval using VisUCyte Antigen Retrieval Reagent-Basic (Catalog # VCTS021). Tissue was stained using DAB (brown) and counterstained with hematoxylin (blue). Specific staining was localized to lymphocytes in germinal center. View our protocol for IHC Staining with VisUCyte HRP Polymer Detection Reagents.

• Reactivity: Hu
• Applications: WB, Flow, IHC, CyTOF-ready
• Clonality: Polyclonal
• Host: Sheep
• Conjugate: Unconjugated
• Concentration: LYOPH

CD21 Antibody [Unconjugated] Summary

• Immunogen: Chinese hamster ovary cell line CHO-derived recombinant human CD21
  Ile21-Arg971
  Accession # P20023
• Specificity: Detects human CD21 in direct ELISAs and Western blots.
• Source: N/A
• Isotype: IgG
• Clonality: Polyclonal
• Host: Sheep
• Gene: CR2
• Purity Statement: Antigen Affinity-purified

Applications/Dilutions

• Dilutions:
  • CyTOF-ready
  • Flow Cytometry 2.5 ug/10^6 cells
  • Immunohistochemistry 3-15 ug/mL
  • Western Blot 0.1 ug/mL

Packaging, Storage & Formulations

• Storage: Use a manual defrost freezer and avoid repeated freeze-thaw cycles.
  • 12 months from date of receipt, -20 to -70 °C as supplied.
  • 1 month, 2 to 8 °C under sterile conditions after reconstitution.
  • 6 months, -20 to -70 °C under sterile conditions after reconstitution.
• Buffer: Lyophilized from a 0.2 μm filtered solution in PBS with Trehalose. *Small pack size (SP) is supplied either lyophilized or as a 0.2 µm filtered solution in PBS.
• Preservative: No Preservative
• Concentration: LYOPH
• Reconstitution Instructions: Reconstitute at 0.2 mg/mL in sterile PBS.

Notes

This product is produced by and ships from R&D Systems, Inc., a Bio-Techne brand.

Alternate Names for CD21 Antibody [Unconjugated]

• C3DR
• C3DRSLEB9
• CD21 antigen
• CD21
• Complement C3d receptor
• complement component (3d/Epstein Barr virus) receptor 2
• complement receptor type 2
• CR2
• EBV receptor
• Epstein-Barr virus receptor

Background

CD21, also known as complement receptor 2 (CR2), is a 145 kDa N-glycosylated member of the RCA (regulators of complement activation) family of proteins. The complement cascade plays an important role in the innate immune system through the recognition and clearance of immune complexes and foreign particles (1). Mature human CD21 contains a 951 aa extracellular domain (ECD) with fifteen tandem SCR/SUSHI repeats, a 28 aa transmembrane segment, and a 34 aa cytoplasmic tail (2, 3). Within the ECD human CD21 shares 67% aa identity with mouse and rat CD21. Human CD21 and CD35 are encoded by two separate genes, but in mouse partially homologous proteins are alternate splice forms of one gene (4). Alternate splicing of human CD21 generates isoforms with an altered SCR8 or an insertion between SCR10 and SCR11 (5). CD21 is primarily expressed on B cells, follicular dendritic cells, and T cells. A circulating soluble form of CD21 is released by proteolytic shedding from activated B cells (6, 7). CD21 binds the complement component fragments iC3b, C3d, and C3d,g (1, 8). It forms a complex with the B cell receptor-associated CD19 molecule and lowers the threshold for B cell activation (9‑11). CD21 can also form complexes with the complement receptor CD35/CR1 (1, 10). Mice deficient in both CD21 and CD35 exhibit normal B cell development but severely compromised germinal center development, antibody production, establishment of protective microbial immunity, and B cell tolerance to self antigens (12, 13). In mice, CD21/CD35 must additionally be present on follicular dendritic cells to mount effective humoral responses and establishment of B cell memory (14). CD21 also binds the gp350 coat protein on Epstein-Barr virus and serves as an uptake receptor for viral infection of B cells (15).

1. Roozendaal, R. and M.C. Carroll (2007) Immunol. Rev. 219:157.
2. Weis, J.J. et al. (1988) J. Exp. Med. 167:1047.
3. Moore, M.D. et al. (1987) Proc. Natl. Acad. Sci. 84:9194.
4. Kurtz, C.B. et al. (1990) J. Immunol. 144:3581.
5. Barel, M. et al. (1998) Mol. Immunol. 35:1025.
6. Masilamani, M. et al. (2003) Eur. J. Immunol. 33:2391.
7. Sengstake, S. et al. (2006) Int. Immunol. 18:1171.
8. Carel, J.-C. et al. (1990) J. Biol. Chem. 265:12293.
9. Matsumoto, A.K. et al. (1991) J. Exp. Med. 173:55.
10. Tuveson, D.A. et al. (1991) J. Exp. Med. 173:1083.
11. Dempsey, P.W. et al. (1996) Science 271:348.
12. Haas, K.M. et al. (2002) Immunity 17:713.
13. Prodeus, A.P. et al. (1998) Immunity 9:721.
14. Rossbacher, J. et al. (2006) Eur. J. Immunol. 36:2384.
15. Tanner, J. et al. (1987) Cell 50:203.

Limitations

This product is for research use only and is not approved for use in humans or in clinical diagnosis. Primary Antibodies are guaranteed for 1 year from date of receipt.

Publications for CD21 Antibody (AF4909)(1)

Publication using AF4909

• Eva-Maria Nichols, Rachel Jones, Rachael Watson, Chris J. Pepper, Chris Fegan, Kevin J. Marchbank A CD21 low phenotype, with no evidence of autoantibodies to complement proteins, is consistent with a poor prognosis in CLL Oncotarget 2015-10-03 [PMID: 26452134]

Bioinformatics

• Gene Symbol: CR2
• Uniprot:
  • P20023(Human)