Absence of the lectin activation pathway of complement does not increase susceptibility to Pseudomonas aeruginosa...

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Pseudomonas aeruginosa is a significant pathogen, particularly in immunocompromised individuals and cystic fibrosis patients.
• The complement system is crucial for innate immunity, with the lectin pathway playing a role in pathogen recognition.

Purpose of the Study:

• To investigate the role of the lectin pathway of complement in immune defense against Pseudomonas aeruginosa.
• To determine if mannan-binding lectin associated serine protease-2 (MASP-2) deficiency impacts P. aeruginosa pneumonia outcomes in a murine model.

Main Methods:

• In vitro complement activation assays were used to assess P. aeruginosa interaction with complement pathways.
• A mouse model of invasive pneumonia was employed, comparing wild-type (WT) and MASP-2 deficient mice.
• Survival rates, serum opsonisation activity, and lung cytokine expression were analyzed.

Main Results:

• Some P. aeruginosa strains activated complement via the lectin pathway in vitro.
• MASP-2 deficient mice showed no significant survival disadvantage compared to WT mice (81.8% vs 72.7%).
• Opsonisation activity and lung cytokine profiles were similar between WT and MASP-2 deficient mice during infection.

Conclusions:

• The lectin pathway, specifically via MASP-2, does not appear to be essential for controlling P. aeruginosa infection in this mouse model.
• These findings suggest alternative complement pathways are more critical for defense against this pathogen in invasive pneumonia.