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Immunochemical quantitation of serum complement components in SFD and AFD infants
Insights
Full-term small-for-date infants often have lower levels of certain complement proteins, including C1q and C5, compared to appropriate-for-date infants. Infant complement levels are generally lower than maternal levels, correlating with gestational age and birth weight.
Area of Science:
- Immunology
- Neonatal Medicine
- Biochemistry
Background:
- The complement system is crucial for innate immunity.
- Understanding complement levels in newborns is vital for assessing immune function.
- Small-for-date (SFD) infants may have altered physiological development.
Purpose of the Study:
- To compare complement component concentrations between full-term SFD and appropriate-for-date (AFD) infants.
- To investigate the relationship between infant and maternal complement levels.
- To examine correlations between whole complement activity and infant characteristics.
Main Methods:
- Measurement of complement protein concentrations (C1q, C3, C3-activator, C4, C5, C9) in infant and maternal sera.
- Assay of whole complement hemolytic activity.
- Comparison of complement levels between SFD and AFD infant groups and their mothers.
Main Results:
- Half of SFD infants exhibited lower C1q and C5 levels compared to AFD infants.
- C3, C3-activator, C4, and C9 levels did not significantly differ between SFD and AFD infants.
- Infant complement component concentrations were consistently lower than maternal levels, with varying infant-maternal ratios.
Conclusions:
- Full-term SFD infants may have a partially compromised complement system, particularly concerning C1q and C5.
- Maternal transfer significantly contributes to infant complement levels.
- Whole complement activity in umbilical cord serum correlates with gestational age and birth weight.
Abstract:
Components of complement (protein concentrations of C1q, C3, C3-activator, C4, C5 and C9 and whole complement (hemolytic activity)) were measured in sera from full-term small-for-date (SFD) and appropriate-for-date (AFD) infants and their mothers. (1) Half the SFD infants showed lower C1q levels than the AFD infants. (2) SFD infants showed the same levels of C3 as AFD infants. (3) Although SFD infants showed slightly higher levels of C3-activator than AFD infants, there was no significant difference. (4) SFD infants and AFD infants showed the same level of C4. (5) With respect to C5, half the SFD infants showed lower levels than the AFD infants. (6) Levels of C9 in the SFD infants were essentially the same as those in the AFD infants. (7) The amount of protein in every complement component of an infant was smaller than that of the mother. In AFD infants, the infant-maternal ratios were 0.64 for C1q, 0.45 for C3, 0.29 for C3-activator, 0.43 for C4, 0.54 for C5 and 0.12 for C9. (8) The whole complement titers of umbilical cord sera from the AFD infants were approximately one half of those of the maternal sera. This is due to the smaller amount of complement protein itself in the infant sera. (9) The whole complement titers of umbilical cord serum agreeably correlate with gestational weeks and birth weight of the infants. (10) The whole complement titer in full-term SFD infants was lower than that in normal full-term AFD infants.