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The normal occurrence of two molecular forms of the eight complement component (C8) and their concentrations in a
Abstract:
A haemolytically inactive alpha-mobile complement C8 component was identified by crossed immunoelectrophoresis in a 27-year-old male with recurrent meningococcal infections and absence of complement mediated serum haemolytic activity. The patient's serum/plasma contained no demonstrable normal C8. C8 inhibitor activity was not demonstrable in his serum and the alternative activation pathway appeared to be intact. Serum from the proband's parents and both siblings had normal total haemolytic complement activity and they were without symptoms. However, both the normal and the haemolytically inactive C8 protein were demonstrable in their sera. Their normal C8 concentrations were less than one-half of the normal C8 mean value and distinctly below the lowest value found in ten healthy persons. The concentration of the inactive C8 component in the proband's serum was roughly 1 . 5 times higher than that of the other family members, whereas its concentration in sera of the family members was between 1 . 8 and 2 . 5 times the highest concentration found in ten healthy donors, all of whom also had an alpha-mobile C8 in measurable quantities.
Insights
A patient with recurrent meningococcal infections lacked functional complement C8 (complement component 8). His family members had reduced normal C8 levels but also an inactive C8 variant, suggesting a genetic link.
Area of Science:
- Immunology
- Complement System Biology
Background:
- The complement system is crucial for innate immunity, with complement component 8 (C8) playing a vital role in the terminal pathway.
- Deficiencies in complement components can lead to increased susceptibility to infections, particularly by Neisseria species.
Observation:
- A 27-year-old male presented with recurrent meningococcal infections and absent complement-mediated serum hemolytic activity.
- Crossed immunoelectrophoresis revealed a haemolytically inactive, alpha-mobile C8 component in the patient's serum, with no detectable normal C8.
Findings:
- The patient's serum lacked normal C8, and C8 inhibitor activity was absent. The alternative complement pathway was intact.
- Family members exhibited normal total hemolytic complement activity but had reduced concentrations of normal C8, alongside the presence of the inactive C8 variant.
- The inactive C8 component was significantly elevated in the patient and present at elevated levels in family members compared to healthy controls.
Implications:
- This case suggests a potential genetic defect leading to the production of a non-functional C8 variant, impacting complement-mediated immunity.
- Understanding the genetic basis of C8 deficiency and variants is critical for diagnosing and managing recurrent infections.
- Further research into the structure and function of this inactive C8 variant could elucidate C8 assembly and its role in the complement cascade.