IL-9 Expression by Invariant NKT Cells Is Not Imprinted during Thymic Development

Area of Science:

• Immunology
• Cellular Biology
• Inflammation Research

Background:

• Invariant natural killer T (iNKT) cells differentiate into distinct effector lineages (NKT1, NKT2, NKT17).
• The developmental pathways and functional roles of IL-9-producing iNKT cells, particularly in mucosal inflammation, are not fully understood.

Purpose of the Study:

• To investigate the conditions and mechanisms regulating IL-9 production in iNKT cells.
• To determine the functional consequences of IL-9-producing iNKT cells in an allergic inflammation model.

Main Methods:

• Induction of IL-9 production in murine and human iNKT cells using TGF-β and IL-4.
• Analysis of IL-9 expression in different iNKT cell subsets (CD4+, NK1.1+, neuropilin-1+).
• Assessment of transcription factor involvement (Irf4, Batf) in IL-9 regulation.
• In vivo studies using adoptive transfer of IL-9+ iNKT cells in a house dust mite-induced allergic airway inflammation model.

Main Results:

• Naive thymic iNKT cells do not express IL-9, but activation with TGF-β and IL-4 induces IL-9 secretion in both murine and human cells.
• IL-9 production can be acquired by various iNKT subsets, suggesting plasticity in functional specialization.
• Irf4 and Batf transcription factors play a crucial role in regulating IL-9 expression in iNKT cells, similar to CD4 T cells.
• Adoptive transfer of IL-9+ iNKT cells exacerbated allergic airway inflammation and promoted granulocyte and mast cell recruitment to the lungs.

Conclusions:

• Peripheral iNKT cells can acquire an IL-9-producing phenotype in response to environmental cues (TGF-β, IL-4).
• IL-9-producing iNKT cells possess proinflammatory functions, mediating allergic inflammation and immune cell recruitment in vivo.
• These findings highlight the plasticity of iNKT cell function and their role in inflammatory responses.