A protective role for the fifth complement component (c5) in allergic airway disease

Area of Science:

• Immunology
• Allergy Research
• Complement System

Background:

• Complement activation, C3a, and C3aR are crucial for Th2 responses in allergic airway inflammation.
• The role of the fifth complement component (C5) in asthma pathogenesis remains largely unevaluated.
• Previous studies link C5 deficiency to increased airway hyperresponsiveness in mice.

Purpose of the Study:

• To investigate the impact of C5 on pulmonary inflammation and Th2 effector functions in a mouse model of experimental asthma.
• To compare C5-sufficient and C5-deficient mice in the context of allergic bronchopulmonary disease.

Main Methods:

• Utilized a mouse model of bronchopulmonary allergy.
• Employed congenic C5-sufficient and C5-deficient mouse strains.
• Assessed airway hyperresponsiveness, inflammatory cell counts (eosinophils), cytokine levels (IL-4, IL-5, IL-13), and IgE levels post-antigen challenge.

Main Results:

• C5-deficient mice showed significantly increased airway hyperresponsiveness compared to wild-type controls.
• A marked increase in airway eosinophils and IL-4-producing cells was observed in C5-deficient mice.
• Elevated levels of Th2 cytokines (IL-5, IL-13) and IgE were found in C5-deficient mice, indicating enhanced allergic inflammation.

Conclusions:

• C5 plays a protective role in experimental allergic lung disease.
• The presence of C5 suppresses inflammatory responses and Th2 effector functions.
• C5a likely mediates this protective effect, suggesting a role in tempering inflammation in Th2-driven diseases like asthma.