Distinct molecular programming governs the expansion of human regulatory and effector CD4+ T cells in response to TCR/IL-2R stimulation

Foreign and self-antigens activate CD4+ conventional and regulatory T cells (Tregs) to promote immunity and tolerance, respectively. These cell populations, which depend on IL-2, are being expanded and engineered in vitro for adoptive cell therapy (ACT) for cancer and autoimmunity. Here, we investigate the molecular pathways underlying the in vitro expansion of human CD4+ Teff and Tregs to TCR/CD28/IL-2 signaling over 12-days. Temporal integration of differential chromatin accessibility and gene expression revealed similar responses over the first 6 days. After this time, Teff cells showed greater expansion that was associated with more robust gene activation and chromatin opening that supported increased activation of mTORC1-dependent signaling and a more energetic phenotype. Thus, Tregs are programmed temporally for more limited expansion in vitro that may benefit ACT for cancer but may be a drawback for autoimmunity. These findings may reflect a mechanism to finely tune Treg numbers to maintain homeostasis in vivo.