Specific serum Ig recognizing staphylococcal wall teichoic acid induces complement-mediated opsonophagocytosis...

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Wall teichoic acid (WTA) from Staphylococcus aureus promotes bacterial colonization.
• The complement system is crucial for pathogen clearance.
• S. aureus WTA binds to mannose-binding lectin (MBL), a lectin pathway component, but adult serum MBL often fails to bind WTA due to inhibitory anti-WTA IgG.

Purpose of the Study:

• To investigate the biological function of human anti-WTA IgG.
• To elucidate the role of anti-WTA IgG in complement activation and opsonophagocytosis of S. aureus.

Main Methods:

• Purification of anti-WTA IgG using a WTA-coupled affinity column.
• Assessment of complement component deposition (C4 and C3) on S. aureus in depleted serum.
• Evaluation of phagocytosis of S. aureus by polymorphonuclear leukocytes.

Main Results:

• Purified anti-WTA IgG, primarily IgG2, induced C4 and C3 deposition on S. aureus in MBL-depleted serum.
• Complement activation was dependent on C1q, indicating classical pathway involvement.
• Anti-WTA IgG-mediated C3 deposition enhanced S. aureus phagocytosis by neutrophils.

Conclusions:

• Human anti-WTA IgG acts as a trigger for classical complement-dependent opsonophagocytosis of S. aureus.
• Antibody-mediated adaptive immunity compensates for MBL deficiency in the lectin complement pathway.
• This highlights the critical role of adaptive immunity in controlling S. aureus infections.