Abstract A015: Thoracic duct cannulation as a new source for CD3+ T cells and other phenotypes used in cell therapies

Abstract Introduction: Adoptive cell therapy using chimeric antigen receptor (CAR) T cells represents a powerful alternative to conventional treatment for lymphoma and leukemia. New approaches to solid tumor treatment using CAR T are under development. Common to all these approaches is the need for patient-derived naïve T cells for CAR T manufacture. The current method for T cell harvest is leukapheresis, a costly and time-consuming effort with a risk of expansion failure due to immune suppression. The purpose of this study was to evaluate direct access of the thoracic duct to harvest T cells for CAR T manufacture and compare cell distribution in thoracic duct lymph vs. peripheral blood. Methods: Approximately 10ml of lymph was aspirated from the thoracic duct using a novel transvascular access/aspiration device through a central venous approach. Peripheral blood samples were taken from patients at the same time. Samples were incubated in Stable-Lyse Stable-Store buffers (SmartTube, Palo Alto CA) according to manufacturer’s instructions. A CyTOF-based phospho-flow assay for PBMCs was performed on each sample without modifications. For each sample 250,000 events were analyzed. Gating was performed in FlowJo (FlowJo LLC, Ashland OR). Results: The following cell/phenotype distributions were observed: CD3+ (lymphocytes) as a percentage of total events: 10% in blood, 75% in lymph. CD3+ (lymphocytes) per 100ul sample: 87,000 in blood, 356,250 in lymph. Dendritic cells (defined as CD4+ HLA-DR+ CD38+) were 401 in blood, 5,700 in lymph. Considering plasmacytoid vs myeloid types, a significantly higher proportion were plasmacytoid in lymph. Finally, naïve B cells were found to be concentrated at 4x peripheral blood. Conclusion: Direct aspiration of thoracic duct lymph represents an improvement over conventional leukapheresis in several ways – reduced time and cost of collection, scalability (fluoroscopic procedures are performed in every hospital, while leukapheresis is not), potential viability, and the ability to collect larger numbers of rare cell types. Naïve & central memory T-cells from circulating lymph exhibit lower inhibitor expression, rapid expansion, superior cytotoxicity, and potentially lower dosing in CAR-T product form. Naïve B cells are critical for emerging B cell engineering (ePCs, eB, eBregs). Because the direct aspiration technique is repeatable, lymph sampling may be used for intermittent post-treatment monitoring, repeat harvesting, or reinfusion. Citation Format: Matthew Callaghan, Christian Eversull, Nandini Venkatesh, Cameron Karamian, Natalia Sigal. Thoracic duct cannulation as a new source for CD3+ T cells and other phenotypes used in cell therapies [abstract]. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr A015.