The study investigates the transfer of microRNAs (miRNAs) from T cells to antigen-presenting cells (APCs) during immune synapse formation. Exosomes, which are vesicles released from cells, were found to contain miRNAs that differ from those in the parent cells. The researchers demonstrated that miRNAs are exchanged between T cells and APCs, with a unidirectional transfer from T cells to APCs mediated by CD63+ exosomes. Inhibition of exosome production impaired miRNA transfer to APCs, and the transferred miRNAs were shown to modulate gene expression in recipient cells. The findings support a mechanism of cellular communication involving antigen-dependent, unidirectional transfer of miRNAs by exosomes during immune synapse formation.The study investigates the transfer of microRNAs (miRNAs) from T cells to antigen-presenting cells (APCs) during immune synapse formation. Exosomes, which are vesicles released from cells, were found to contain miRNAs that differ from those in the parent cells. The researchers demonstrated that miRNAs are exchanged between T cells and APCs, with a unidirectional transfer from T cells to APCs mediated by CD63+ exosomes. Inhibition of exosome production impaired miRNA transfer to APCs, and the transferred miRNAs were shown to modulate gene expression in recipient cells. The findings support a mechanism of cellular communication involving antigen-dependent, unidirectional transfer of miRNAs by exosomes during immune synapse formation.