Airway epithelium expresses interleukin-18

Area of Science:

• Immunology
• Respiratory Medicine
• Cytokine Biology

Background:

• Interleukin-18 (IL-18) is a cytokine involved in inflammatory responses.
• Its role in pulmonary inflammation, particularly concerning T-helper (Th)1 and Th2 responses, requires further investigation.

Purpose of the Study:

• To investigate the pulmonary expression of IL-18 in the context of Th1 and Th2 immune responses.
• To examine IL-18 regulation in mouse models of LPS and ovalbumin (OVA) challenge and in human sarcoidosis and asthma.

Main Methods:

• In situ hybridization and immunocytochemistry were employed to quantify cells expressing IL-18, IFN-gamma, IL-5, and MBP in mouse lung tissue and human bronchial biopsies.
• Analysis included control groups, LPS-treated mice (Th1 model), OVA-challenged mice (Th2 model), and patients with sarcoidosis and asthma.

Main Results:

• IL-18 was localized to airway epithelium and mononuclear cells, with constitutive expression in normal lungs and controls.
• LPS challenge increased IL-18 mRNA and IFN-gamma positive cells, indicative of a Th1 response.
• OVA challenge showed decreased IL-18 mRNA positive cells but increased IL-5 and MBP positive cells, characteristic of a Th2 response.
• Human studies revealed increased IL-18 in sarcoidosis and decreased IL-18 in asthma tissues compared to controls.

Conclusions:

• Interleukin-18 is expressed in the airway epithelium.
• Pulmonary IL-18 expression is regulated by both Th1 and Th2 immune responses.
• These findings highlight IL-18's role in airway inflammation and its differential regulation in conditions like sarcoidosis and asthma.