CD4+FoxP3+ T regulatory cells subsets release small extracellular vesicles containing cell death-related proteins as potential mechanism of T cell suppression

Introduction: (iTregs). Methods: iTregs produced with TGF-β or with TGF-β plus retinoic acid (RA) (RATregs). Results: culture of splenocytes with sEV showed induction of cell death/apoptosis, which is enhanced when adding sEV obtained from nTregs and RATregs, and not from iTregs. Proteomic analysis on sEV obtained from Tregs subsets revealed 163 common proteins, of which some share Tregs biology-related functions such as Apolipoprotein AI, Integrin β2, Lactate Dehydrogenase-A, Thrombospondin 1 and Transferrin Receptor. Depending on the combination of Tregs subsets analyzed, 5 major clusters containing cell death-related proteins were identified, including molecules belonging to the Granzyme/Perforin pathway. Discussion: Although this study does not explain the enhanced cell death observed in cultures with sEV produced by nTregs and RATregs, it does demonstrate that Tregs subsets produce sEV with inhibitory function driven -at least- by cell death, providing new insights on the biology of Tregs.