Th memory for interleukin-17 expression is stable in vivo.

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• T helper (Th) cells are crucial for adaptive immunity, with distinct subsets like Th1, Th2, and Th17 defined by cytokine production.
• Th1 and Th2 cells exhibit imprinted cytokine gene expression via transcription factors T-bet and GATA-3, respectively.
• Th17 cells express Interleukin-17 (IL-17) and rely on transcription factors RORgammat and RORalpha.

Purpose of the Study:

• To investigate the stability and plasticity of IL-17 memory in Th17 cells.
• To determine if Th17 cells maintain their distinct lineage identity under various culture conditions.

Main Methods:

• Development of a cytometric IL-17 secretion assay for isolating viable IL-17-secreting Th cells.
• In vitro generation and culture of Th17 cells under different cytokine signaling conditions (TGF-beta/IL-6, IL-23, Interferon-gamma, IL-4, IL-12).
• Isolation and in vitro culture of ex vivo-generated Th17 cells.

Main Results:

• In vitro-generated Th17 cells require continuous TGF-beta/IL-6 or IL-23 signaling for IL-17 expression and can be converted to Th1 or Th2 cells by IL-12 or IL-4, respectively.
• Ex vivo-isolated Th17 cells maintain IL-17 memory in vitro, independent of IL-23, IL-12, or IL-4 signaling.
• This indicates cytokine memory in ex vivo Th17 cells is stable and not regulated by Th1/Th2 polarizing cytokines.

Conclusions:

• Th17 cells generated in vivo represent a stable and distinct lineage of T helper cell differentiation.
• The plasticity observed in vitro does not reflect the inherent stability of Th17 cells in an in vivo context.
• Understanding Th17 cell stability is critical for developing targeted immunotherapies.