Complement activation in newborn infants with early onset infection

Area of Science:

• Immunology
• Neonatal Medicine
• Host Defense Mechanisms

Background:

• The complement system is crucial for host defense.
• Neonates exhibit quantitative complement deficiencies and decreased C3 levels.
• Knowledge regarding complement activation products in newborns is limited.

Purpose of the Study:

• To investigate complement activation products in healthy neonates, those with maternal or neonatal colonization, and those with early-onset infection.
• To assess the role of complement activation in neonatal infections.

Main Methods:

• Prospective study analyzing EDTA plasma from 32 healthy term neonates, 41 neonates with maternal colonization, 15 colonized neonates, and 10 neonates with early-onset infection.
• Quantification of C3a-desArg using a novel ELISA.
• Measurement of C3bBbP (alternative pathway convertase) and C1rsC1-inactivator (classical pathway activation product) via double-sandwich ELISA.
• Determination of C3 levels using radial immunodiffusion.

Main Results:

• Plasma C3a-desArg levels were similar in healthy neonates and adults, but C3 levels were diminished in newborns.
• No significant differences in complement activation products were observed between healthy, colonized, and maternally colonized neonates.
• Neonates with infection showed significantly elevated C3a-desArg at disease onset, linked to alternative pathway activation.
• C1rsC1-inactivator complex levels did not differ significantly across study groups.

Conclusions:

• Elevated C3a-desArg in infected neonates suggests alternative pathway activation contributes to severe neonatal infections.
• Anaphylatoxin C3a's inflammatory properties may be significant in neonatal infection pathogenesis.
• Further research is warranted to elucidate the precise role of complement activation in neonatal sepsis.