IL-2 secretion-based sorting of single T cells using high-throughput microfluidic on-cell cytokine capture

using step emulsification, enabling processing of entire libraries of cells within tens of minutes without significant secretion crosstalk. In comparison to our approach, strong mitogenic activation overwhelmed the conventional bulk on-cell cytokine assay, rendering labeled, non-activated cells indistinguishable from actively secreting neighbors within one hour. Processing of identical cell mixtures following droplet encapsulation yielded no apparent crosstalk even after three hours. Instead, IL-2 production spanning several orders of magnitude was observed from roughly 20% of analyzed activated lymphocytes, representing an at least 10-fold increase in dynamic range compared to unencapsulated cells. Secreting cells could also be sorted using fluorescence activated cell sorting (FACS). The approach can ultimately enable sorting of cells based on functional properties with higher accuracy in a more accessible format to life science researchers.