The invention in various aspects provides for magnetic enrichment and/or expansion of antigen-specific T cells, allowing for identification and characterization of antigen-specific T cells and their T cell receptors (TCRs) for therapeutic and/or diagnostic purposes, as well as providing for production of antigen-specific engineered T cells for therapy. Incubation of paramagnetic nano-aAPCs in the presence of a magnetic field, either during enrichment and/or expansion steps, activates T cells through magnetic clustering of paramagnetic particles on the T cell surface.
