Conventional CD4+ T cells regulate IL-22-producing intestinal innate lymphoid cells

Area of Science:

• Immunology
• Gastroenterology
• Microbiome research

Background:

• The intestine relies on innate and adaptive immunity for barrier integrity and microbiota regulation.
• The specific crosstalk between these immune systems in maintaining gut homeostasis is not fully understood.

Purpose of the Study:

• To investigate the regulatory role of CD4+ T cells in the innate immune system of the intestine.
• To elucidate the mechanisms by which CD4+ T cells influence barrier-protective innate lymphoid cells (ILCs) and antimicrobial peptide (AMP) production.

Main Methods:

• Utilized RAG1-/- and MHCII-/- mice models lacking T and B cells or CD4+ T cells, respectively.
• Employed cell transfer experiments and genetically modified mice to track immune cell function.
• Analyzed the expression of interleukin-22 (IL-22) and AMPs (Reg3γ, Reg3β) in response to immune cell populations.

Main Results:

• Mice lacking CD4+ T cells exhibited increased ILC numbers, IL-22 production, and AMP expression.
• CD4+ T cell transfer corrected these elevations, indicating a negative regulatory role.
• T-cell receptor-dependent mechanisms mediated by CD4+ T cells were responsible for reducing IL-22 levels.

Conclusions:

• CD4+ T cells play a critical role in negatively regulating intestinal ILCs and AMPs at a steady state.
• This highlights a novel mechanism of CD4+ T cell-mediated control over the IL-22-AMP axis in the gut.
• Understanding this crosstalk is crucial for maintaining intestinal homeostasis and barrier function.