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

IntroductionT regulatory cells (Tregs) are pivotal for immune tolerance. Among the suppression mechanisms attributed to Tregs, the release of small extracellular vesicles (sEV) has been proposed with CD73, Nrp1 and the transfer of key miRNAs playing a key role.

Although these findings have been described for natural Tregs (nTregs), little is known on Tregs induced in vitro (iTregs).MethodsHere, we characterized sEV production from three types of Tregs: nTregs and in vitro iTregs produced with TGF-β or with TGF-β plus retinoic acid (RA) (RATregs).ResultsCharacterization of sEV production indicates that all Tregs produce sEV with similar size and presence of Alix and Tsg101, with RATregs showing the highest production of sEV. Regarding sEV function, nTregs, iTregs and RATregs produce sEV that suppress CD4+ T and CD8+ T cell proliferation.

Interestingly, in vitro 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.