Fc-free soluble dimer proteins enable sensitive and specific detection of CAR-T cells by directly measuring antigen binding to the CAR. Unlike traditional linker-based detection methods that only confirm CAR surface expression, antigen-based detection evaluates functional target recognition, providing a more biologically relevant assessment of CAR-T cell activity.
Designed for flow cytometry applications, Fc-free dimer antigens help reduce nonspecific background staining, improve signal-to-noise ratio, and support reliable CAR-T characterization across a wide range of assay conditions.
Applications include:
CAR linker detection methods often rely on antibodies against CAR linker regions or framework sequences. While useful for measuring CAR expression, these methods do not confirm whether the CAR is functional or capable of binding its intended target antigen.
Using a CAR-specific target antigen, such as recombinant CD19 protein for detection of CD19 CAR-T cells, offers significant advantages because it directly measures functional CAR binding.
Because antigen-binding frequency and fluorescence intensity often correlate with CAR-T functionality, antigen-based detection is increasingly preferred for:
Fc-containing detection reagents can interact with Fc receptors expressed on immune cells including monocytes, NK cells, macrophages, and activated lymphocytes. These Fc receptor interactions may generate nonspecific background staining and complicate flow cytometry interpretation, particularly in complex samples such as PBMCs or whole blood.
Conigen’s Fc-free dimer antigens are designed to eliminate Fc receptor-mediated interactions while maintaining strong, high-avidity CAR binding.
The dimeric antigen format also provides enhanced avidity, enabling sensitive detection of both high- and low-affinity CAR-T cells.
| CAR-T Detection Feature | Use Fc-Free Dimer Antigen |
|---|---|
| Functional binding | Yes |
| Specificity | High |
| Sensitivity | High |
| Fc receptor binding | No |
| Potency assessment | Yes |
| Flow signal/gating | Clean |
| PBMC compatibility | Yes |
| Fc blocking needed | Often no |
Fc-free dimeric CD19 protein was used to detect CD19-CAR–expressing CD4+ and CD8+ T cells by flow cytometry. Human primary T cells transfected with CD19-CAR mRNA, or left untransfected, were stained with His-tagged dimeric CD19 and analyzed by flow cytometry.
CAR-bound CD19 dimer was detected using an APC-conjugated anti-His antibody. Untransfected T cells and no-antigen controls showed no detectable signal, demonstrating sensitive and specific detection of CAR-T cells by CD19 dimer.
Key Observations
| Product | Tag | Species | Product Code | Details | hf:tax:product_tag | hf:tax:pa_species |
|---|---|---|---|---|---|---|
| CD4, Protein Dimer | His | All Species, Human | CSP-24004 | Show details | his | all-species human |
| CD19, Protein Dimer | His | All Species, Mouse | CSP-124-01 | Show details | his | |
| TROP-2, Protein Dimer | Flag-His | All Species, Human | CSP-24041-02 | Show details | flag-his | |
| Siglec 6, Protein Dimer | His | All Species, Human | CSP-25203-01 | Show details | his | |
| CD19, Protein Dimer | His | All Species, Human | CSP-24125-01 | Show details | his | all-species human |
| B7H3 isoform 4lg, Protein Dimer | His-Avi | All Species, Human | CSP-240984lg | Show details | his-avi | |
| B7H3 isoform 2lg, Protein Dimer | His-Avi | All Species, Human | CSP-240982lg | Show details | his-avi | |
| CD117, Protein Dimer | His-Avi | All Species, Rhesus Macaque | CSP-25194-03 | Show details | his-avi | |
| CD117, Protein Dimer | His-Avi | All Species, Mouse | CSP-25193-03 | Show details | his-avi | |
| VEGFR2, Protein Dimer | His-Avi | All Species, Human | CSP-25127-03 | Show details | his-avi | |
| FGFR4, Protein Dimer | His-Avi | All Species, Human | CSP-25132-03 | Show details | his-avi | |
| Nectin-4, Protein Dimer | His | All Species, Human | CSP-24016 | Show details | his | |
| CD19, Protein Dimer | His-Avi | All Species, Human | CSP-24125-03 | Show details | his-avi | |
| CD38, Protein Dimer | His-Avi | All Species, Human | CSP-24096-03 | Show details | his-avi | |
| Siglec 3, Protein Dimer | His | All Species, Human | CSP-25200-01 | Show details | his | |
| CD19, Protein Dimer | His | All Species, Cynomolgus/Rhesus Macaque | CSP-25291-01 | Show details | his | |
| CD4, Protein Dimer | His | All Species, Rhesus Macaque | CSP-24038 | Show details | his | |
| CD117, Protein Dimer | His-Avi | All Species, Human | CSP-24123-03 | Show details | his-avi | |
| ROR1, Protein Dimer | His | All Species, Human | CSP-25287 | Show details | his | |
| TROP-2, Protein Dimer | Flag-His | All Species, Mouse | CSP-25191-02 | Show details | flag-his | |
| CD117, Protein Dimer | hFc | All Species, Human | CSP-25123-04 | Show details | hfc | |
| CD4, Biotinylated Protein Dimer | His-Avi | All Species, Human | BCSP-24004-03 | Show details | his-avi | |
| CD4, Protein Dimer | His-Avi | All Species, Human | CSP-24004-03 | Show details | his-avi | |
| CD19, Biotinylated Protein Dimer | His-Avi | All Species, Human | BCSP-24125-03 | Show details | his-avi |
CAR-T Cell Characterization
Identify and quantify functional CAR-expressing populations with high specificity.
Potency Assessment
Evaluate biologically relevant antigen binding associated with CAR-T functionality.
Clinical Monitoring
Support persistence and monitoring studies using sensitive antigen-based detection.
PBMC-Compatible Assays
Reduce Fc receptor-mediated background in complex immune cell samples.
Flow Cytometry Workflow Simplification
Reduce or eliminate Fc-blocking requirements for streamlined assay workflows.
Antigen-based CAR-T detection uses the CAR’s target antigen to directly measure functional CAR binding rather than simply detecting CAR surface expression.
Linker detection confirms the presence of the CAR construct, while antigen-based detection confirms functional target recognition and binding capability.
Fc-free dimers eliminate Fc receptor-mediated interactions that can cause nonspecific background staining and interfere with flow cytometry analysis.
Yes. The dimeric format provides enhanced avidity that supports sensitive detection of both high- and low-affinity CAR-T cells.
Conigen Bioscience supplies Fc-free soluble dimer antigens for CAR-T detection and flow cytometry applications, including targets such as CD19, CD22, CD33, CD38, B7H3, ROR1, TROP-2, and others. Products are available in multiple species formats and detection tags to support CAR-T characterization, potency assessment, and assay development workflows.
Conigen’s Fc-free soluble dimer proteins provide a highly specific and biologically relevant approach for CAR-T detection, characterization, and assay development.
Interested in implementing Fc-free antigen-based CAR-T detection in your workflow?
Poster Presented at Cancer Immunotherapy Keystone Symposia March 15-18, 2026 Fairmont Le Château Frontenac, Québec, QC, Canada Abstract CD19-directed chimeric antigen receptor T (CAR-T) cell
Transcript Modern CAR-T workflows depend on CD19 that preserves its native ectodomain structure and has reliable high-affinity binding. CAR expression detection scFv generation and screening
CD19 Proteins CD19 is a type I transmembrane glycoprotein in the immunoglobulin superfamily expressed on B cells throughout development and widely used as a marker
