Distinct roles for B cell-derived LTα3 and LTα1β2 in TNF-mediated ileitis

Area of Science:

• Immunology
• Gastroenterology
• Inflammatory Bowel Disease Research

Background:

• Crohn's disease involves tumor necrosis factor (TNF) and TNF receptors.
• B cells produce ligands for TNF receptors, including Lymphotoxin-alpha (LTα).
• LTα forms membrane-bound LTαβ₂, promoting tertiary lymphoid tissue, and soluble LTα₃.

Purpose of the Study:

• To investigate the role of B cell-derived LTαβ₂ and LTα₃ in Crohn's disease ileitis.
• To determine the specific contributions of these ligands to disease pathology in TNF^ΔARE+/- mice.

Main Methods:

• Utilized TNF^ΔARE+/- mouse model for Crohn's disease.
• Generated B cell-specific LTβ knockout mice to assess LTαβ₂ function.
• Administered neutralizing antibodies against LTα₃ to evaluate its effects.
• Monitored intestinal permeability, IgA+ plasma cells, cytokine levels, and body/muscle mass.

Main Results:

• B cell-specific LTβ deletion was necessary for tertiary lymphoid tissue but minimally impacted ileitis.
• Loss of B cell-derived LTα significantly increased intestinal permeability and reduced IgA+ plasma cells.
• B cell-derived LTα deficiency led to weight loss, muscle mass reduction, and elevated cytokines.
• Neutralizing LTα₃ exacerbated TNF-driven cachexia-like symptoms.

Conclusions:

• B cell-derived LTαβ₂ and LTα₃ have distinct and independent roles in experimental ileitis.
• LTα₃, not LTαβ₂, is critical for maintaining intestinal barrier integrity and preventing cachexia.
• Soluble LTα₃ exhibits a protective function by counterbalancing TNF-induced pathology in the intestine.