CYTO 2026 Scientific Tutorial: Decoding CAR T Dynamics: Flow Cytometry–Driven Insights from Autologous and Allogeneic Trials

Decoding CAR T Dynamics: Flow Cytometry–Driven Insights from Autologous and Allogeneic Trials

Presenters:
Nithianandan Selliah, PhD, Global Director Flow cytometry, Cerba Research
Bieke Soen, PhD, Senior Scientist Flow cytometry, Cerba Research

Abstract:
Chimeric Antigen Receptor T-cell (CAR T) therapy has revolutionized the treatment of hematologic malignancies and is showing increasing promise in solid tumors. Both autologous and allogeneic CAR T-cell products are now advancing through clinical trials and therapeutic use. CAR T cells are genetically engineered T cells that express a chimeric antigen receptor (CAR), which recognizes a specific antigen on tumor cells, thereby redirecting immune specificity and enhancing cytotoxicity. This tutorial provides a foundational overview of CAR T trial design, emphasizing the critical role of flow cytometry in monitoring CAR T-cell kinetics, persistence, and immunophenotypic changes in patients.  

Autologous CAR T cells are patient-derived genetically modified T cells, whereas allogeneic CAR T cells are healthy donor-derived genetically modified T cells.  While autologous CAR T cells minimize immune rejection, they face challenges in manufacturing time, product variability, and cell quality in heavily pretreated patients. Conversely, allogeneic CAR T cells offer “off-the-shelf” scalability without treatment delay, but pose risks of graft-versus-host disease (GvHD) and host immune rejection. These differences necessitate distinct flow cytometric strategies for product validation and patient monitoring.

Flow cytometry remains the gold standard for tracking CAR T-cell expansion, persistence, and phenotype during clinical evaluation. The tutorial outlines essential gating strategies for accurate identification of CAR T populations. In autologous trials, CAR⁺CD3⁺ cells are identified within the patient’s T-cell compartment using CAR-specific antibodies. However, in allogeneic CAR T trials, where TCRαβ is knocked out and CD3 expression is absent, CAR⁺ cells must be detected within the CD3⁻ compartment, requiring alternative gating and additional markers. Initial gating involves selecting singlets and viable lymphocytes via forward and side scatter, excluding dead cells with viability dyes, and identifying CD3⁺ and CD3⁻ populations. CAR expression is confirmed using reagents such as fluorochrome-labeled anti-idiotype antibodies, Protein L, or construct-incorporated tags (e.g., EGFRt, truncated CD19). In allogeneic trials, correctly distinguishing CAR⁺CD3⁻ cells from host immune cells is critical.

A unique challenge in allogeneic CAR T studies is the standard TBNK (T-cell, B-cell, NK-cell) assay’s limitation in accurately enumerating NK cells. In these patients, the CD3⁻ compartment includes CD19⁺ B cells, CD16/56⁺ NK cells, and CAR⁺ T cells. We present alternative panel design and a modified gating strategy to properly distinguish host NK cells from CD3- CAR T-cells that possibly express CD56 upon activation.

Flow cytometry’s strengths—high sensitivity, multiparametric resolution, and simultaneous assessment of activation, exhaustion, and memory phenotypes—make it indispensable in CAR T trials. This tutorial equips researchers and clinical scientists with practical, technology-focused guidance for standardized flow cytometric analysis, enabling accurate immune monitoring, data harmonization, and informed therapeutic assessment.

By the end of the session, participants will gain actionable insights into assay design, gating logic, and troubleshooting for both autologous and allogeneic CAR-T trials, enhancing precision in immune monitoring and data interpretation across clinical and research settings.

Learning Objectives
By the end of this tutorial, participants will be able to:

1. Differentiate between autologous and allogeneic CAR T-cell products and understand how their biological and manufacturing differences influence flow cytometry–based monitoring strategies.

2. Design and optimize flow cytometry panels for the detection and characterization of CAR T cells in patients with autologous and allogenic trials, including appropriate marker selection and reagent use (e.g., Protein L, anti-idiotype antibodies, tag-based detection).

3. Apply appropriate gating strategies to accurately identify CAR T-cell populations in both CD3⁺ (autologous) and CD3⁻ (allogeneic, TCR-knockout) compartments while minimizing misclassification and background signal.

4. Recognize challenges in standard immunophenotyping assays (e.g., TBNK panels) when analyzing samples from patients treated with allogeneic CAR T and implement modified gating and marker strategies to improve NK-cell enumeration.

5. Interpret CAR T-cell flow cytometry data to assess expansion, persistence, activation, and exhaustion phenotypes, supporting standardized immune monitoring and harmonized data analysis in clinical trials.

Keywords: Clinical Applications, Immune Cell Cytometry, Car-T Cells

CMLE Credit: 1.5