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Complement and immunoglobulin levels in early childhood in homozygous sickle cell disease
Insights
Children with sickle cell disease show lower complement component C3 levels and higher C3d levels early in life, suggesting increased complement system activity. This study questions the role of individual complement deficiencies in infection susceptibility in young sickle cell patients.
Area of Science:
- Immunology
- Hematology
- Pediatrics
Background:
- Sickle cell disease (SS) is associated with immune dysregulation.
- Understanding early immune system changes in SS disease is crucial for managing complications.
Purpose of the Study:
- To investigate complement component and immunoglobulin levels in infants and young children with sickle cell disease (SS) compared to healthy controls (AA genotype).
- To explore the relationship between complement levels and infection prevalence in early childhood SS disease.
Main Methods:
- Longitudinal study of 63 children with SS disease and 88 children with normal haemoglobin (AA) genotype from birth to 2 years.
- Measurement of complement component levels (C3, C4, factor B) and functional assays.
- Quantification of immunoglobulin levels (IgA, IgM, IgG).
Main Results:
- Consistently lower C3 levels and significantly higher C3d levels observed in SS children from early life, indicating increased C3 turnover.
- No significant genotype differences in C4, factor B levels, or functional assays.
- Elevated IgA levels noted in SS disease at 2 years, but no consistent patterns for IgM or IgG.
Conclusions:
- Increased complement C3 turnover occurs early in life in sickle cell disease.
- Findings suggest that individual complement deficiencies may not be the primary driver of infection susceptibility in very young children with SS disease.
Abstract:
Complement levels, tests of complement function, and immunoglobulin levels were studied in 63 children with homozygous sickle cell (SS) disease and in 88 children with a normal haemoglobin (AA) genotype from birth to 2 yr of age. Levels of complement component C3 were consistently lower in SS children, the difference being highly significant (p less than 0.001) by the age of 2 yr and levels of C3d were significantly higher from the age of 6 months. These observations are compatible with increased turnover of C3 in SS disease from early in life. No consistent genotype differences were observed in the levels of C4, factor B, or functional assays. IgA levels in SS disease were significantly higher at age 2 yr but there were no consistent patterns with IgM or IgG. There was no difference in the prevalence of infections between groups with low C3 or low values of alternative pathway activity but the groups were small and only capable of detecting major differences. However, the findings cast some doubt on the role of individual complement deficiencies in the susceptibility to infection in SS children at this age.