Affinity Barrier in Antigen-Specific T Cell Capture
Identifying and isolating rare, antigen-specific T lymphocytes has been a central challenge in both research and clinical immunotherapy. T cell receptors (TCRs) typically bind to peptide-MHC (pMHC) complexes with very low affinity (dissociation constants of 10⁻⁴ to 10⁻⁶ M). While multimeric pMHC probes have been used to amplify this weak signal, they often suffer from a tradeoff between sensitivity and specificity. High-avidity probes can non-specifically engage off-target T cells, limiting their clinical utility.
Live antigen-presenting cells (APCs) offer an alternative, but they come with their own problems—namely, stochastic antigen processing, continuous MHC turnover, and difficulties in storage and reproducibility. These issues make it hard to consistently present the desired antigens for specific T cell targeting.
Nature has evolved a solution to the weak TCR-pMHC interaction: the immunological synapse (IS). The IS is a specialized cell–cell junction formed between T cells and APCs, enabling stable, long-lived contact even with weak binding affinities. This contact zone is characterized by the organization of receptors into supramolecular activation clusters (SMACs), actin cytoskeletal rearrangement, and membrane exchange processes like trogocytosis.
We leveraged this natural phenomenon by creating polymerized antigen-presenting cells (pAPCs)—cell-like constructs with preserved membrane protein function but enhanced stability through intracellular hydrogelation. These pAPCs retain essential surface molecules (e.g., MHC-I, CD80, CD86, ICAM-1) and mimic live-cell interactions to induce bona fide IS formation. The result: improved selectivity and functional engagement of cognate T cells, without the drawbacks of live cells.
Polymerized Cellular System
The development of polymerized antigen-presenting cells (pAPCs) builds upon extensive research efforts devoted to engineering biomimetic cell–gel hybrid systems through photo-activated intracellular polymerization. This innovative approach enables live cells to be infused with photopolymerizable monomers and polymerized from the inside out using light-triggered chemistry. The result is a robust cell-gel construct that retains the structural integrity of the cytoplasm while preserving the fluidity and native organization of the plasma membrane.
Crucially, the preservation of the membrane allows these hybrid cells to maintain biologically relevant interactions at the cell surface—such as immunological synapse formation with T cells. This capability has made the platform broadly applicable beyond immune cell capture. In previous studies, cell-gel hybrids have been successfully used in tissue engineering as scaffolding components, in pathogen neutralization as decoys, in membrane protein isolation for proteomics, and in synthetic biology to build modular cellular interfaces1-5.
In this study, we adapted this platform for immune applications by generating pAPCs from dendritic cells pre-loaded with superparamagnetic nanoparticles. After polymerization, the pAPCs demonstrated exceptional stability (e.g., withstanding lyophilization and rehydration), long-term antigen display via kinetically driven peptide replacement, and selective T cell engagement mimicking live-cell dynamics.
By combining the mechanical durability of synthetic hydrogels with the biological specificity of living cells, this cell-gel hybrid system offers a powerful and tunable strategy for T cell capture and other cell–cell interaction studies.
Applications in Anticancer and Antiviral T Cell Capture
This platform has profound implications for cancer immunotherapy and antiviral research. In tumor-bearing mouse models, pAPCs loaded with tumor antigens effectively enriched tumor-reactive CD8+ T cells, significantly enhancing their cytotoxic activity and therapeutic outcomes when used in adoptive cell therapy.
In parallel, pAPCs enabled the detection of elusive neoantigen-specific T cells—targets that often go undetected by conventional tetramer staining due to their rarity and low affinity. Using pAPCs, we were able to enrich T cells specific to neoantigens like Adpgk and Reps1 in MC38 tumor-bearing mice after immune checkpoint blockade.
Human applications were also demonstrated. we engineered monoallelic HLA-A02:01-expressing HEK293T cells into pAPCs capable of presenting viral antigens such as CMV pp65. From peripheral blood of CMV-seropositive human donors, pp65-specific CD8+ T cells were successfully isolated. Additionally, pAPCs loaded with MART-1 antigen enriched melanoma-specific T cells from HLA-A02:01 transgenic mice, which exhibited potent cytotoxicity against human melanoma cells in vitro.
Future Prospect in Biomaterials and Immunotherapy
This study introduces a new generation of biomimetic probes that combine the structural fidelity of live cells with the modularity and stability of synthetic systems. By harnessing the immunological synapse and overcoming the inherent limitations of passive pMHC-based probes, polymerized APCs provide a robust, scalable, and versatile solution for antigen-specific T cell capture.
Their ability to stably present diverse antigens, induce genuine T cell activation, and allow for magnetic purification of functional lymphocytes positions this technology as a valuable tool for both basic immunology and clinical translation—particularly in the age of personalized cancer vaccines and T cell therapies.
As synthetic biology and materials science continue to converge, the cell–gel hybrid platform may well become a cornerstone in immune diagnostics, adoptive immunotherapy, and neoantigen discovery.
For more, read the full paper here