CD127low

CD127low describes cells that express low levels of CD127, the interleukin-7 receptor alpha chain (IL-7Rα), on their surface. CD127 is part of the receptor for interleukin-7 and participates in signaling pathways that support T cell survival, homeostasis, and development. In humans, CD127 expression is often assessed by flow cytometry to help define T cell subsets.

In the context of CD4+ T cells, the CD127low phenotype is most closely associated with regulatory T cells (Tregs). The conventional phenotypic combination used to identify human Tregs in peripheral blood and tissues is CD4+CD25highCD127lowFOXP3+. The CD127low status helps distinguish Tregs from conventional activated T cells, which can transiently alter CD127 expression but do not typically express FOXP3. Functional Tregs characterized by the CD127low phenotype are generally suppressive and contribute to immune tolerance and the prevention of autoimmunity.

CD127 expression is not fixed and can vary with activation, cytokine milieu, and tissue context. As a result, CD127low is a useful, but context-dependent, marker in both research and clinical studies. Changes in the proportion or function of CD127low regulatory T cells have been investigated in autoimmune diseases, infections, cancer, and transplant settings, where they may correlate with disease activity or responses to therapy.

Overall, CD127low serves as an informative identifier for a regulatory T cell–enriched subset in humans and is employed to improve the characterization of immune cell composition in health and disease.