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Synthesis of two components of human complement, beta 1H and C3bINA, during fetal life
Insights
Complement component levels, including beta 1H and C3bINA, increase with gestational age in human fetuses. Fetal liver and peritoneal cells synthesize beta 1H, indicating its production during development.
Area of Science:
- Immunology
- Developmental Biology
- Human Physiology
Background:
- The complement system is crucial for immune responses and development.
- Understanding complement component levels during fetal development is essential for assessing immune competence.
- Beta 1H and C3bINA are key regulators of the complement cascade.
Purpose of the Study:
- To quantify beta 1H and C3bINA levels in human fetal, cord, and maternal sera.
- To investigate the relationship between gestational age and complement component concentrations.
- To determine the site of beta 1H synthesis during fetal development.
Main Methods:
- Serum sample collection from human fetuses, newborns, and mothers.
- Quantification of complement components (beta 1H, C3bINA, C9, Factor B) using immunological assays.
- Detection of newly synthesized beta 1H in cultured fetal cells (liver, peritoneal) via amino acid incorporation and immunoprecipitation.
Main Results:
- Beta 1H and C3bINA were detectable in fetuses >12 weeks old, with levels increasing with gestational age.
- Cord sera showed approximately 54% (beta 1H) and 61% (C3bINA) of adult mean levels.
- Maternal sera exhibited elevated beta 1H, C9, and Factor B levels near term, while fetal/newborn sera had low C9.
- Newly synthesized beta 1H was identified in fetal liver and peritoneal cell cultures.
Conclusions:
- Complement components beta 1H and C3bINA are produced during human fetal development.
- Complement system maturation occurs progressively throughout gestation.
- Fetal liver and peritoneal cells are sites of beta 1H synthesis, contributing to its presence in fetal circulation.
Abstract:
The levels of beta 1H and C3bINA were estimated in sera from human fetuses, cord and maternal samples. Both components of complement were detected in fetuses more than 12 weeks old. The serum concentrations tended to increase with the gestational age. The mean levels of beta 1H and C3bINA in cord sera were near 54 and 61% of the mean values in sera from normal adults. Elevated levels of beta 1H were observed in maternal sera at the end of the gestational period. When the levels of beta 1H and C3bINA were compared with those of two other components of complement, it was confirmed that the mean levels of C9 were low in fetal and newborn sera, while the serum concentrations of both C9 and Factor B were elevated in maternal samples. Newly synthesised beta 1H was detected in the culture fluids of fetal liver and peritoneal cells, as judged by the incorporation of labelled aminoacids and the autoradiography of he specific immunoprecipitates in agar gel.