Fig. 1: Preparation and characterization of magnetized pAPCs.

A A schematic illustrating the preparation of magnetized polymerized antigen-presenting cells (pAPCs) and their attributes for immunological synapse-mediated antigen-specific T cell capture. Created in BioRender. Chen, H. (2025) https://BioRender.com/qyctluuB A schematic illustrating the binding affinity and binding specificity relationship for T cell engagement the passive probes containing multimeric ligands or with cellular targets through immunological synapse formation. C Bright-field microscopic observations of live JAWSII and magnetized pAPCs under isotonic buffer (PBS) and hypotonic buffer (water). Scale bar = 100 μm. The experiment was independently repeated three times. D Transmission electron microscopy images showing the presence of iron-oxide nanoparticles in pAPCs. Arrows indicate the iron-oxide nanoparticles in the cytoplasm. The experiment was independently repeated three times. Scale bar = 100 nm. E Quantification of magnetized pAPCs immediately following preparation and following a single round of magnetic enrichment. The error bars represent mean ± standard deviation. P values from top to bottom, ****p < 0.0001, **p = 0.0049 (Independent biological replicates n = 3). F Images showing pAPCs undergoing magnetically induced clustering. G Examination of surface proteins, including H-2kb, CD80, CD86, and ICAM1 on live APC and pAPCs by flow cytometric analysis. Hollow and solid gray histograms indicate isotype controls with live APCs or pAPCs, respectively. H Images showing lyophilized and water-reconstituted pAPCs. I Flow cytometric examination of surface proteins, including H-2kb, CD80, CD86, and ICAM1 on pAPCs following 180 days of storage by lyophilization. The error bars represent mean ± standard deviation. P values from left to right. NS p = 0.5630, NS p = 0.5588, NS p = 0.1688, NS p = 0.0657 (Independent biological replicates n = 3). Statistical analyses were performed by two-sided Student’s t tests.