PE-Labeled CD19 His Tag: The "Universal Fluorescent ID Card" of the B-Cell World
Author: Senior Product Manager of UA Views：522 
PE-Labeled CD19 His Tag is a core B-lymphocyte-specific detection probe, specifically designed for the precise identification, quantification, and analysis of all mature B cells and their precursors.
- Recent Advances
- Product Information
Recent Advances
PE-Labeled CD19 His Tag is a core B-lymphocyte-specific detection probe designed for precise identification, quantification, and analysis of all mature B cells and their precursors. Its core functionality combines CD19—the most widespread and stable surface marker of B cell lineage—with a high-brightness phycoerythrin (PE) fluorescent reporting system, providing researchers with a high-intensity, highly specific tool to "illuminate" the entire B cell family within complex cellular mixtures. Serving as an indispensable "molecular ID card" reader, it plays vital roles in fundamental immunology research, clinical hematological tumor diagnosis, immune monitoring, and cell therapy applications.
I. Overview: Molecular Design, Structure, and Functional Modules
This protein is a recombinant single-chain or multi-domain fusion protein engineered for optimal target binding and signal output. It typically comprises three key functional components:
CD19 Binding Module
The core of the probe usually consists of the single-chain variable fragment (scFv) of an anti-human CD19 monoclonal antibody or an engineered CD19 ligand domain. CD19 is a 95 kDa transmembrane glycoprotein belonging to the immunoglobulin superfamily. It begins expression at the earliest stage of B cell development (pre-B cell stage) and persists throughout all mature B cells until differentiation into plasmablasts, making it the most reliable lineage marker for pan-B cells. It participates in forming the B cell receptor complex and regulates B cell activation thresholds.
His Tag
A polyhistidine sequence located at the protein terminus. Its primary functions include:
Simplified purification: Enables efficient, highly specific purification via nickel column affinity chromatography, ensuring high activity and batch-to-batch consistency.
Facilitated immobilization and conjugation: Allows directional immobilization of the probe onto biosensor chips, microbeads, or solid surfaces for functional studies or detection array construction.
PE Fluorescent Label
R-phycoerythrin is stably conjugated to the protein via chemical coupling. PE is a multichromophore polymeric protein that emits intense orange/red fluorescence (~575 nm) when excited by 488-561 nm lasers.
Ultra-high brightness: PE is one of the strongest fluorescent dyes in flow cytometry, with signal intensity far exceeding small-molecule dyes like FITC, delivering exceptional signal-to-noise ratios.
Broad compatibility: Its emission spectrum makes it ideal for multicolor flow cytometry paired with FITC, PerCP, APC, etc., compatible with nearly all flow cytometers and fluorescence microscopes.
Working Principle Overview
This probe functions like a "high-visibility ID card scanner" specifically designed for B cells. The anti-CD19 scFv acts as the "scanning head" that precisely recognizes the unique "ID number" (CD19) of B cells; PE serves as the "high-brightness display" that converts recognition information into an unmistakable orange optical signal; while the His tag functions as the "precision adjustment knob" during production and optimization.
II. Core Mechanism: High-Intensity, Lineage-Specific B Cell Labeling
The probe's core application mechanism relies on the lineage specificity of CD19 antigen to achieve high-intensity fluorescent labeling of the entire B cell population.
1. High Affinity and Pan-B Cell Coverage
Comprehensive B cell detection: From bone marrow pre-B cells and immature B cells to peripheral blood/lymphoid tissue naïve B cells, memory B cells, follicular/marginal zone B cells, and even plasmablasts—all express CD19. Thus, this probe labels virtually the entire B cell lineage, serving as the gold standard for B cell enumeration and proportional analysis.
High-affinity binding: The anti-CD19 module exhibits high affinity, forming stable complexes with cell-surface CD19 even in complex samples (e.g., whole blood, bone marrow, tissue-derived cells), ensuring robust labeling.
2. PE's Ultra-Brightness Advantages
Exceptional signal-to-noise ratio: PE's extreme brightness enables clear distinction between CD19low B cell precursors and negative populations, reducing gating subjectivity and improving accuracy/reproducibility.
Ideal for low-expression samples and rare subset analysis: For B cells with downregulated CD19 (e.g., post-immunosuppressive therapy) or specific developmental stages, PE's brightness ensures reliable detection and facilitates identification/sorting of rare subsets (e.g., regulatory B cells).
Anchor channel in multicolor panels: Due to its strong, stable signal, PE-CD19 is often the "anchor" channel in multicolor flow cytometry, first defining the total B cell gate before analyzing other markers.
3. Extended Applications of His Tag
Functionalized surfaces and analysis: Immobilized probes can study interactions with soluble CD19 protein or CD19 in cell lysates.
Quality control: His tag detection aids in analyzing probe concentration and integrity.
III. Downstream Applications: A Core Tool in B Cell Biology and Medicine
This probe has extensive applications, serving as a cornerstone in B cell-related research and clinical practice.
1. Fundamental Immunology Research
B cell development tracking: Combined with CD10, CD20, CD34, IgM, IgD, etc., it precisely stages B cell development in bone marrow and extramedullary environments.
Core component of immunophenotyping: In clinical/research immunophenotyping, CD19 paired with CD3 and CD16/CD56 defines the three major lymphocyte classes (T, B, NK cells). This probe is the preferred reagent for this critical classification.
B cell function and activation studies: Combined with activation markers (CD25, CD69, CD86) and differentiation markers (CD27, CD38), it analyzes B cell activation states and differentiation during immune responses.
2. Diagnosis, Classification, and Monitoring of B Cell Malignancies
Universal marker for B cell lymphomas/leukemias: Nearly all B cell-derived malignancies express CD19, including CLL, ALL, DLBCL, follicular lymphoma, mantle cell lymphoma, etc. Thus, this probe is decisive for diagnosing B cell tumors and distinguishing them from T cell/myeloid tumors.
Key for minimal residual disease (MRD) detection: Post-treatment for B-ALL/CLL, high-sensitivity multicolor flow cytometry (using PE-CD19 as a core marker) detects rare residual tumor cells in bone marrow/peripheral blood—a gold standard method for assessing treatment depth and predicting relapse risk.
Differential diagnosis: Helps distinguish CD19-negative plasma cell tumors (e.g., multiple myeloma) from CD19-positive B cell malignancies.
3. Immune Deficiency and Autoimmune Disease Evaluation
Primary immunodeficiencies: In X-linked agammaglobulinemia (XLA, caused by BTK mutation leading to B cell developmental block), peripheral B cell (CD19+ cell) counts are severely reduced/absent. This probe is crucial for screening/diagnosis.
Secondary immunodeficiency and immune monitoring: Tracks B cell reconstitution kinetics post-chemotherapy, immunosuppressants (e.g., rituximab), or hematopoietic stem cell transplantation.
Autoimmune disease research: Analyzes quantity, proportion, and functional state changes of B cell subsets in peripheral blood/tissues of SLE, RA, etc. patients.
4. Cell Therapy Research and Development
Cornerstone tool for CD19-CAR-T therapy:
Target validation: Confirms CD19 expression levels on patient tumor cells—a prerequisite for CD19-CAR-T eligibility.
Efficacy monitoring: Post-treatment, tracks CD19+ B cell (normal/malignant) clearance—a direct indicator of CAR-T functional activity in vivo.
Detecting CD19-negative escape: At relapse, identifies clones with downregulated/lost CD19 expression.
B cell sorting: Combined with anti-PE magnetic beads or direct flow sorting, obtains high-purity CD19+ cells for adoptive therapy or in vitro studies.
IV. Future Perspectives: Integration, Quantification, and Companion Diagnostics
As a classic tool, its future lies in enhancing information dimensionality, quantitative precision, and clinical decision integration.
Absolute Quantification and Antigen Density Analysis
Quantitative flow cytometry: Using PE-quantified beads to calibrate fluorescence intensity into absolute CD19 molecules/cell—critical for pre-CAR-T target density assessment and ADC efficacy prediction.
High-Parameter Flow and Single-Cell Multiomics Integration
Spectral/mass cytometry: Developing CD19 detectors for spectral/mass cytometry (with rare metal tags) to better resolve B cell heterogeneity in ultrahigh-parameter (>30-color) analyses.
CITE-seq applications: DNA-barcoded CD19 antibodies (same epitope) combined with transcriptomics enable simultaneous surface protein and whole-transcriptome profiling at single-cell resolution.
Spatial Biology and Tissue In Situ Analysis
Optimized probes for multiplex IF/IHC (e.g., CODEX, PhenoCycler) reveal spatial distributions of CD19+ B cells in lymphoid/tumor/autoimmune tissues—their spatial relationships with Tfh cells, germinal centers, vasculature, etc.—uncovering immune functional niches.
Companion Diagnostics and Point-of-Care Testing
Leveraging its core recognition function to develop standardized, simplified flow/lateral flow assays for clinical labs to rapidly quantify B cells—serving as companion diagnostics for immune status evaluation or targeted therapy (e.g., anti-CD20 drugs) efficacy.
Live-Cell Imaging and Functional Dynamics
Utilizing PE's brightness for time-lapse imaging to observe CD19 aggregation, endocytosis, and redistribution during immune synapse formation, cell migration, or intercellular interactions.
Summary
PE-Labeled CD19 His Tag is a paradigmatic tool in immunology and hematology. It marries B cells' fundamental lineage identifier—CD19—with one of the most vivid optical reporting systems—PE—creating a powerful, reliable, and universal "B cell fluorescent ID card." From mapping healthy B cell development to diagnosing complex malignancies; from monitoring immune balance to enabling revolutionary CD19-CAR-T therapies, this probe remains an indispensable "compass" for researchers and clinicians. As single-cell technologies, spatial omics, and precision medicine advance, CD19 detection will evolve toward higher dimensions, precise quantification, and deeper clinical integration—continuing its irreplaceable role in unraveling immune mysteries and combating disease.
```
This article is reviewed and published by the technical expert team of UA
Disclaimer: This article partially utilizes artificial intelligence assistance in its creation. If any content involves copyright or intellectual property issues, please let us know and we promise to verify and remove it as soon as possible.
Purchase recombinant protein, choose Nanjing UA-Bio
UA protein focuses on providing various protein reagents, raw materials, and services required for drug research and development, cell therapy, gene therapy, and basic scientific research, including drug target proteins, immune checkpoint proteins, cytokines, tool enzymes, customized protein expression, and full-length transmembrane protein development. Youai is committed to providing customers with high-quality products and professional services, and building a High-tech Biological Enterprise with International Competitiveness.
Target proteins | membrane proteins | cytokines | enzymes | viral antigens | protein customization
Nanjing UA Biotechnology Co., Ltd. Email：order@ua-bio.com Phone：+86-25-56221161
Product Information
Link：
©2021-2026 all rights reserved UA Biotechnology Co.,Ltd.
Privacy Policy 
网站备案号 浙ICP备2022019033号-2 浙公网安备33010202004867号
Business license (three certificates in one) Tel：+86-25-56221161
E-mail：order@ua-bio.com
All products sold on this website shall not be used for clinical diagnosis or treatment of humans or animals, and shall only be used for non-medical purposes such as industrial or scientific research.
