[Perspective] Converting to adapt
Effective immune responses rely on balancing lymphocyte stability and plasticity. Lymphocytes have regulatory circuits that control phenotypic and functional identity. Stable circuits maintain homeostasis and prevent autoimmunity. But plasticity is needed to integrate new environmental inputs and generate immune responses that subdue the eliciting agent without damaging tissue. Regulatory T cells (Tregs) are a subset of CD4+ T cells that control effector T cell responses and prevent excessive inflammation and autoimmunity (1, 2). On page 1581 in this issue, Sujino et al. (3) report that intestinal Tregs convert into CD4+ intraepithelial T cells (CD4IELs) to adapt to the local intestinal environment, thus identifying the intestinal epithelium as a compartment that enforces lymphocyte plasticity. Authors: Marco Colonna, Luisa Cervantes-Barragan