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Ultrasensitive discrimination mediated by the dynamic immunological synapse (IS) formation between T lymphocytes and cognate cellular targets has inspired live cell-based strategies for antigen-specific T cell identification. However, unpredictable antigen presentation associated with antigen processing and major histocompatibility complex (MHC) turnover can limit the specificity and utility of these live cell-based lymphocyte probes. Herein, we demonstrate a cell-mimicking lymphocyte capture strategy using intracellularly polymerized antigen presenting cells (pAPCs), which permit modular and persistent antigen presentation upon kinetically driven antigen loading. pAPCs undergo cell-like engagement with cognate T cells, eliciting hallmarks of bona fide IS formation such as supramolecular activation cluster (SMAC) patterns, cytoskeletal contraction of engaged T cells, and trogocytosis. Magnetization of pAPCs through incorporation of superparamagnetic nanoparticles enables label-free magnetic isolation of cognate T cells, and the biomimetic lymphocyte capture strategy exhibits superior sensitivity and specificity to conventional MHC-conjugated magnetic beads. From the splenocytes of tumor-burden hosts, pAPC-mediated capture of tumor-reactive lymphocytes is demonstrated to enhance adoptive T cell therapy and improve identification of neoantigen-specific T cells. Lastly, we show adaptation of intracellular polymerization to genetically engineered cells expressing monovalent human MHC, which enable enrichment of virus- and tumor-specific CD8 T cells from human PBMCs and humanized transgenic mice. The study demonstrates advances in cell-gel hybrid system towards enhancing antigen-specific T cell identification.

Key words: Intracellular polymerization, antigen-specific T cell capture, immunological synapse

Taiwan International Graduate Program in Molecular Medicine,
National Yang-Ming University and Academia Sinica
Doctoral Dissertation