IL-7 improves the fitness of regulatory T cells for adoptive transfer

Adoptive regulatory T cell (Treg) trasfer represents a potential therapeutic option to control immune responses in organ transplantation, graft vs host disease, and autoimmunity, including type 1 diabetes. Treg for adoptive therapy are traditionally sorted and expanded in vitro with high doses of IL-2, showing stability and suppressive capacity, but with some limitations in terms of long-term survival once infused in patients. Here, we tested a novel expansion protocol in which we added IL-7 (IL-7 method, IL-7M) to the traditional standard method (StM) using IL-2. We showed that naïve Treg express significant levels of CD127 and robustly respond to IL-7 by phosphorylating STAT-5. Naive Treg expanded with the IL-7M were highly enriched in CD45RA CD62L CD95 showing a reduction in the final cell yield and suppressive function. Treg expanded with the IL-7M preserved telomere length and were more resistant to cytokine withdrawal and fas-mediated apoptosis. Overall our data indicate that it is possible to expand naïve Treg in the presence of IL-7 to generate a final Treg product enriched in poorly differentiated CD45RA cells and with better resistance to stress and apoptosis, potentially improving the long-term survival of Treg in adoptive transfer protocols.