MHC class II antigen presentation by intestinal epithelial cells fine-tunes bacteria-reactive CD4 T-cell responses

Area of Science:

• Immunology
• Gastroenterology
• Cell Biology

Background:

• Intestinal epithelial cells (IECs) express Major Histocompatibility Complex class II (MHC II), particularly during inflammation.
• The role of IEC-mediated antigen presentation in shaping CD4+ T cell immunity during intestinal infections is not fully understood.

Purpose of the Study:

• To investigate the impact of IEC MHC II expression on CD4+ T cell responses and disease outcomes in the context of enteric bacterial infections.
• To determine if IECs act as antigen-presenting cells and modulate T cell immunity.

Main Methods:

• Selective gene ablation of MHC II in IECs.
• In vitro co-culture systems using colonic IEC organoids and CD4+ T cells.
• In vivo studies with adoptively transferred antigen-specific CD4+ T cells during bacterial infection.

Main Results:

• Intestinal bacterial infections upregulate MHC II processing and presentation molecules in colonic IECs.
• IEC MHC II expression did not significantly alter disease severity in Citrobacter rodentium or Helicobacter hepaticus infections.
• IECs activate antigen-specific CD4+ T cells in an MHC II-dependent manner, modulating both regulatory and effector T helper cell subsets.
• In vivo, IEC MHC II expression was found to dampen pro-inflammatory effector T helper cells.

Conclusions:

• IECs function as non-conventional antigen-presenting cells during intestinal inflammation.
• IEC MHC II expression plays a crucial role in fine-tuning local effector CD4+ T cell responses, dampening inflammation.