IL-15-dependent balance between Foxp3 and RORγt expression impacts inflammatory bowel disease

Area of Science:

• Immunology
• Cell Biology
• Gastroenterology

Background:

• CD4+ T cell plasticity contributes to autoimmune disease risk.
• Interleukin-15 (IL-15) is a pleiotropic cytokine with immunomodulatory functions.
• The balance between regulatory T cells (Treg) and T helper 17 (Th17) cells is critical in intestinal inflammation, such as in inflammatory bowel disease (IBD).

Purpose of the Study:

• To investigate the role of IL-15 in modulating the functional commitment of CD4+ T cells, specifically Treg (expressing Foxp3) and Th17 (expressing RORγt) cells.
• To elucidate the impact of IL-15 on the development of IBD in a mouse model.

Main Methods:

• Utilized a mouse model to study the effects of IL-15 delivery to CD4+ T cells in the colon.
• Assessed the expression of transcription factors Foxp3 and RORγt, and associated signaling pathways (STAT5 phosphorylation, Runx1 expression).
• Measured the production of pro-inflammatory cytokines (interferon-γ, IL-6) and the accumulation of Th1/Th17 cells in the context of IBD.

Main Results:

• Impaired IL-15 delivery to colonic CD4+ T cells led to decreased Foxp3 expression (reduced STAT5 phosphorylation) and increased RORγt expression (upregulated Runx1).
• CD4+ T cells deprived of IL-15 rapidly induced IBD in mice.
• IBD development was characterized by elevated pro-inflammatory cytokine production (IFN-γ, IL-6) and an increased presence of Th1/Th17 cells.

Conclusions:

• IL-15 plays a protective role in IBD by maintaining the balance between Treg and Th17 cell populations.
• Modulating IL-15 signaling in the gut may be a therapeutic strategy for controlling intestinal inflammation.
• Fine-tuning the Treg/Th17 balance via IL-15 is essential for preventing the exacerbation of IBD.