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Some aspects of the humoral immunity and the phagocytic function in newborn infants
1Department of Pediatrics, Sapir Medical Center (Meir Hospital), Kfar Saba, Israel.
Insights
Newborns, especially premature infants, have weaker immune systems. Their complement system and neutrophil function are impaired, increasing infection risk.
Area of Science:
- Immunology
- Neonatal Medicine
- Complement System Biology
Background:
- Neonatal infants, particularly preterm infants, exhibit increased susceptibility to severe pyogenic infections.
- Existing research indicates deficiencies in humoral immunity and neutrophil phagocytic activity in newborns.
Purpose of the Study:
- To comprehensively evaluate complement function and component levels in newborns compared to adults.
- To investigate the impact of neonatal and adult serum on neutrophil bactericidal activity.
Main Methods:
- Assessed complement function (CH50, AP50) and levels of complement components (Clq, Clr, Cls, C2-C9, FB, properdin) in preterm, full-term infants, and adults.
- Examined the effect of autologous and heterologous serum on neutrophil bactericidal activity by cross-matching newborn and adult components.
Main Results:
- Newborns (preterm and full-term) demonstrated significantly impaired complement activity (CH50, AP50) and reduced complement component levels compared to adults.
- Complement component levels, excluding C7, correlated positively with gestational age but not birthweight.
- Neutrophil bactericidal activity in full-term newborns was markedly reduced (one-third of adult levels), with adult serum significantly enhancing it, indicating a humoral defect.
Conclusions:
- Both humoral and phagocytic immune functions are demonstrably impaired in newborn infants.
- These immune deficiencies likely contribute to the heightened vulnerability of neonates to severe pyogenic infections.
Abstract:
Newborn infants, particularly those born prematurely, are prone to develop life-threatening pyogenic infections. Different studies have demonstrated impairment of various aspects of the humoral immunity and the phagocytic activity of neutrophils in newborns. We conducted a comprehensive study evaluating the complement function (CH50 and AP50) and the level of the vast majority of the complement components (Clq, Clr, Cls, C2-C9, FB and properdin) in preterm and full-term newborn infants as compared to adults. Furthermore, we investigated the effect of autologous and heterologous serum on the bactericidal activity of neutrophils, by crossing newborn serum with adult cells and vice versa. Results showed that preterm and full-term newborns have an impaired complement activity as compared to adults (CH50 P < 0.05, AP50 < 0.01) and significantly reduced complement components except for C7, which was found to be normal in full-term infants and in most appropriate-for-gestational age preterm newborns at 34-36 weeks. A statistically significant correlation was found between gestational age and the level of most of the complement components. CH50 and AP50 also showed a positive trend which, however, was not statistically significant. No correlation was found between birthweight and complement activity or complement component levels. The neutrophil bactericidal activity of full-term newborns was about one-third that of adults (P < 0.001). Adult serum improved the bactericidal activity of newborn neutrophils by 93%, indicating a considerable neonatal humoral defect. Conversely, neonatal serum blunted the adult bactericidal activity by 86%. Our results support the fact that both humoral and phagocytic functions in newborn infants are impaired, which may possibly account for their increased tendency to develop severe pyogenic infections.