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Complement in chronic secretory otitis media. C3 breakdown and C3 splitting activity
Abstract:
Occurrence of in vivo C3 breakdown and in vitro C3 splitting activity was studied in serum and middle-ear effusion (MEE) samples from 30 children with chronic secretory otitis media (SOM). The MEE showed strongly elevated levels of both low- and high-molecular-weight C3 breakdown products, along with decreased factor B, C4, and C3 levels. Total hemolytic complement component activity was virtually absent from MEE. The MEE fluids were found to contain C3 splitting factors as demonstrated by their high capacity to convert C3 in vitro from fresh normal human serum. This activity was not inhibited by the classic complement pathway inhibitor, 0.01M ethylene glycol tetra-acetic acid with 0.005M magnesium chloride. The results suggest that a strong local complement activation has taken place and that the factors responsible are present in the MEE of patients with SOM.
Insights
This study found complement system activation in middle-ear fluid from children with secretory otitis media (SOM). The fluid contained factors that split complement component C3, indicating local immune responses in SOM.
Area of Science:
- Immunology
- Otolaryngology
- Biochemistry
Background:
- Secretory otitis media (SOM) is a common condition in children.
- The role of the complement system in SOM pathogenesis is not fully understood.
Purpose of the Study:
- To investigate the occurrence of complement component C3 breakdown and C3 splitting activity in middle-ear effusion (MEE) from children with SOM.
- To identify factors responsible for complement activation within the MEE.
Main Methods:
- Analysis of serum and MEE samples from 30 children with SOM.
- Measurement of C3 breakdown products, factor B, C4, and C3 levels.
- Assay for C3 splitting activity in MEE using normal human serum.
- Testing the effect of a classic complement pathway inhibitor.
Main Results:
- MEE showed elevated C3 breakdown products and decreased levels of C3, C4, and factor B.
- Total hemolytic complement activity was absent in MEE.
- MEE contained factors that split C3 in vitro, independent of the classic complement pathway.
Conclusions:
- Strong local complement activation occurs in the middle ear of patients with SOM.
- Factors responsible for C3 splitting are present within the MEE, suggesting an intrinsic pathway of activation.