Frontiers in Immunology (Dec 2021)

IL-15Rα-Independent IL-15 Signaling in Non-NK Cell-Derived IFNγ Driven Control of Listeria monocytogenes

  • Madhuparna Nandi,
  • Mitterrand Muamba Moyo,
  • Sakina Orkhis,
  • Jeanne Masunga Faida Mobulakani,
  • Marc-André Limoges,
  • Fjolla Rexhepi,
  • Marian Mayhue,
  • Anny Armas Cayarga,
  • Gisela Cofino Marrero,
  • Subburaj Ilangumaran,
  • Subburaj Ilangumaran,
  • Alfredo Menendez,
  • Alfredo Menendez,
  • Sheela Ramanathan,
  • Sheela Ramanathan

DOI
https://doi.org/10.3389/fimmu.2021.793918
Journal volume & issue
Vol. 12

Abstract

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Interleukin-15, produced by hematopoietic and parenchymal cells, maintains immune cell homeostasis and facilitates activation of lymphoid and myeloid cell subsets. IL-15 interacts with the ligand-binding receptor chain IL-15Rα during biosynthesis, and the IL-15:IL-15Rα complex is trans-presented to responder cells that express the IL-2/15Rβγc complex to initiate signaling. IL-15-deficient and IL-15Rα-deficient mice display similar alterations in immune cell subsets. Thus, the trimeric IL-15Rαβγc complex is considered the functional IL-15 receptor. However, studies on the pathogenic role of IL-15 in inflammatory and autoimmune diseases indicate that IL-15 can signal independently of IL-15Rα via the IL-15Rβγc dimer. Here, we compared the ability of mice lacking IL-15 (no signaling) or IL-15Rα (partial/distinct signaling) to control Listeria monocytogenes infection. We show that IL-15-deficient mice succumb to infection whereas IL-15Rα-deficient mice clear the pathogen as efficiently as wildtype mice. IL-15-deficient macrophages did not show any defect in bacterial uptake or iNOS expression in vitro. In vivo, IL-15 deficiency impaired the accumulation of inflammatory monocytes in infected spleens without affecting chemokine and pro-inflammatory cytokine production. The inability of IL-15-deficient mice to clear L. monocytogenes results from impaired early IFNγ production, which was not affected in IL-15Rα-deficient mice. Administration of IFNγ partially enabled IL-15-deficient mice to control the infection. Bone marrow chimeras revealed that IL-15 needed for early bacterial control can originate from both hematopoietic and non-hematopoietic cells. Overall, our findings indicate that IL-15-dependent IL-15Rα-independent signaling via the IL-15Rβγc dimeric complex is necessary and sufficient for the induction of IFNγ from sources other than NK/NKT cells to control bacterial pathogens.

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