CD21 FITC

Overview

CD21 FITC is a Mouse monoclonal targeting CD21, supplied as a FITC format for FC workflows. It supports measurement of Human target expression in common experimental systems.

Key elements and design rationale

• Clone: HB5 — consistent clone identity can support panel reproducibility and cross-study comparisons.
• Isotype: IgG2a — informs selection of matched controls and secondary reagents when relevant.
• Conjugate: FITC — enables direct detection in fluorescence-based assays. Excitation is typically matched to Blue (488nm) lasers in cytometer configurations.
• Host species: Mouse — useful for panel design and control strategy planning.
• Reactivity: Human — interpret staining in the context of species-specific sequence and expression differences.

Key specifications such as clone identity, isotype, and fluorophore conjugation help researchers align panel design, control selection, and instrument configuration with the biological question and sample type.

Biological background

The mouse monoclonal antibody produced by clone HB5 binds to complement receptor 2 (CR2), known as CD21, a 145 kDa glycoprotein of the complement control protein family. It is a receptor for the complement components C3d and C3g and, under pathological circumstances, for the Epstein-Barr virus (EBV). As complement breakdown fragments remain bound to the agent initiating the complement activation in the first place, CD21 plays an important role in the uptake of immunocomplexes. In addition, it plays a role in B cell development and activation as well as memory B cell survival. Thus, it is a key component in developing and maintaining humoral immune response to T-dependent antigens. CD21 associates with CD19, CD81 and the B cell receptor. The cell surface marker CD21 is expressed on mature B cells and follicular dendritic cells. It is used as a cell marker for the phenotyping of leukemias.

Research relevance and current trends

• High-parameter immunophenotyping: combining CD21 with complementary lineage and activation markers to resolve complex cell states.
• Panel standardization and data comparability: increasing emphasis on consistent reagents, compensation-aware fluorophore choices, and shared gating strategies.
• Integration with single-cell multi-omics: pairing surface marker profiling with transcriptomic or proteomic readouts to connect phenotype to function.

Common research applications

• Flow cytometry: quantify CD21-positive populations and compare expression distributions across conditions or time points.
• Cell sorting: enrich CD21-defined subsets for downstream RNA/protein assays or functional readouts.

Changes in measured signal are typically interpreted in the context of cell subset frequency, activation/differentiation state, and sample processing effects rather than as a standalone readout.

Notes for experimental interpretation

• Fluorophore selection: consider brightness, spectral overlap, and instrument configuration; compensation and spillover can affect apparent population boundaries.
• Biology-driven confounders: activation state, differentiation, and isoform/PTM variation can shift epitope accessibility and apparent expression.
• Control concepts: include matched isotype and fluorescence-minus-one (FMO) controls where appropriate, and interpret results alongside biological positive/negative reference samples.

For antibody-based assays, monoclonal versus polyclonal format can influence epitope recognition breadth and signal consistency. Conjugated antibodies support direct detection and can simplify multicolor panel design when paired with appropriate controls and instrument settings.

Customization & Add-ons: Can’t find the antibody you need—or require a custom format for your assay? We can help you source the best match or support custom antibody solutions for diverse research needs, including species and isotype selection, conjugations and labeling (e.g., HRP/AP, biotin, fluorophores), purification grade options (Protein A/G, affinity purified), formulation preferences (buffer selection, carrier-free, glycerol-free), custom concentrations and aliquoting, low-endotoxin options for cell-based work, and application-focused QC/validation support (project dependent). Click Talk to a Scientist to submit a request, email us at support@biohippo.com, or explore our Research Services for additional support—our team will follow up with feasibility details and next steps.