Host defense against Neisseria meningitidis requires a complement-dependent bactericidal activity

Area of Science:

• Immunology
• Microbiology
• Complement System

Background:

• Severe or recurrent Neisseria infections are linked to deficiencies in terminal complement components (C5-C9).
• The terminal attack sequence of complement is crucial for host defense against bacterial pathogens.

Purpose of the Study:

• To investigate the role of the terminal complement attack sequence in host defense against Neisseria species.
• To assess the impact of complement component 8 (C8) deficiency on bactericidal activity.

Main Methods:

• Utilized the C-11 strain of Neisseria meningitidis.
• Employed human serum genetically deficient in complement component 8 (C8-D serum).
• Compared C8-D serum with normal serum in functional assays including leukocyte ingestion, intracellular killing, and fluid-phase bactericidal activity.

Main Results:

• C8-D serum supported leukocyte-mediated ingestion and intracellular killing of Neisseria meningitidis similarly to normal serum.
• C8-D serum exhibited significantly reduced fluid-phase bactericidal activity against Neisseria meningitidis compared to normal serum.
• Reconstitution of C8-D serum with C8 restored normal serum's bactericidal capacity.

Conclusions:

• Serum complement-dependent bactericidal activity, particularly involving complement component 8, is critical for host defense against invasive Neisseria species.
• Deficiency in terminal complement components compromises the ability to clear Neisseria infections.