IL-9 orchestrates immune regulation through CD39/CD73 dependent metabolic reprogramming

Adenosine triphosphate (ATP), a principal component of cellular energy metabolism, also functions as a significant extracellular signaling molecule under pathological conditions, including tissue damage and inflammation. The hydrolysis of extracellular ATP (eATP) to adenosine, catalyzed by ectonucleotidases including CD39 and CD73, is a key pathway involved in the control of immune responses. The objective of this study was to systematically examine the capacity of interleukin-9 (IL-9) to regulate ATP-adenosine metabolism and to assess the resultant impact of this regulation on T-cell responses. Peripheral blood mononuclear cells (PBMCs) isolated from healthy donors were analyzed by flow cytometry (FC) and ELISA to characterize the phenotypic, functional, and metabolic changes induced by IL-9 and to investigate the underlying molecular mechanisms. Our findings revealed that while IL-9 did not significantly change the frequency of major T-cell populations, it potentiated the conversion of ATP to adenosine by upregulating the expression of CD39 and CD73. This activity fostered an immunosuppressive microenvironment, especially within regulatory T (Treg) cells. Furthermore, IL-9 treatment suppressed the production of pro-inflammatory cytokines, increased anti-inflammatory cytokine levels, and inhibited T-cell proliferation. The pharmacological inhibition of CD39 and CD73 largely abrogated these IL-9-mediated effects. Together, these findings suggest that IL-9 may act as a regulator of the CD39/CD73 axis and that its influence on ATP-adenosine metabolism may have relevance in inflammatory and immune-mediated conditions characterized by dysregulated purinergic signaling.