Antigen-Specific T Cell Detection via Photocatalytic Proximity Cell Labeling (PhoXCELL)

Quantitative
detection and characterization of antigen-specific
T cells are crucial to our understanding of immune responses as well
as the development of new immunotherapies. Herein, we report a spatiotemporally
resolved method for the detection and quantification of cell–cell
interactions via Photocatalytic proXimity CELl Labeling (PhoXCELL). The biocompatible photosensitizer dibromofluorescein
(DBF) was leveraged and optimized as a nongenetic alternative of enzymatic
approaches for efficient generation of singlet oxygen upon photoirradiation
(520 nm) on the cell surface, which allowed the subsequent labeling
of nearby oxidized proteins with primary aliphatic amine-based probes.
We demonstrated that DBF-functionalized dendritic cells (DCs) could
spatiotemporally label interacting T cells in immune synapses via
rapid photoirradiation with quantitatively discriminated interaction
strength, which revealed distinct gene signatures for T cells that
strongly interact with antigen-pulsed DCs. Furthermore, we employed
PhoXCELL to simultaneously detect tumor antigen-specific CD8+ as well as CD4+ T cells from tumor-infiltrating lymphocytes
and draining lymph nodes in murine tumor models, enabling PhoXCELL
as a powerful platform to identify antigen-specific T cells in T cell
receptor (TCR)-relevant personal immunotherapy.