Antigen-presenting ILC3 regulate T cell-dependent IgA responses to colonic mucosal bacteria

Area of Science:

• Immunology
• Microbiology
• Gastroenterology

Background:

• Intestinal immune homeostasis relies on host-microbiota interactions.
• Immunoglobulin A (IgA) shapes the gut commensal composition.
• Mechanisms controlling T cell-dependent IgA responses are not fully understood.

Purpose of the Study:

• To investigate the role of group 3 innate lymphoid cells (ILC3) in regulating T cell-dependent IgA responses.
• To elucidate how ILC3 modulate T follicular helper (TfH) and B cell interactions.
• To understand ILC3's contribution to intestinal immune homeostasis.

Main Methods:

• Studied ILC3 localization and function in intestinal draining lymph nodes.
• Investigated ILC3-mediated regulation of TfH and B cell responses.
• Analyzed IgA coating of colonic bacteria in the presence and absence of ILC3-intrinsic antigen presentation.

Main Results:

• ILC3 reside in lymph nodes and limit TfH responses and B cell class switching via antigen presentation.
• Absence of ILC3-intrinsic antigen presentation leads to increased IgA coating of colonic bacteria.
• ILC3 act as a regulatory checkpoint for T cell-dependent IgA generation.

Conclusions:

• Lymph node-resident, antigen-presenting ILC3 are critical regulators of T cell-dependent colonic IgA.
• ILC3 maintain intestinal homeostasis and mutualism with the commensal microbiota.
• ILC3 control the magnitude and quality of mucosal IgA responses.