Functionally active complement proteins C6 and C7 detected in C6- and C7-deficient individuals.

Area of Science:

• Immunology
• Complement System Biology

Background:

• Complement proteins C6 and C7 are crucial components of the terminal complement pathway.
• Deficiencies in these proteins can impact immune function and susceptibility to infections.

Purpose of the Study:

• To develop sensitive ELISAs for detecting complement proteins C6 and C7.
• To investigate the presence and function of C6 and C7 in individuals with diagnosed deficiencies.
• To assess the formation of the terminal complement complex (TCC) in these individuals.

Main Methods:

• Development of two sensitive sandwich ELISAs using monoclonal antibodies against native C6 and C7.
• Quantitation of C6 and C7 in serum samples from deficient individuals.
• Assay of terminal complement complex (TCC) formation after complement activation.

Main Results:

• Detection of C6 and/or C7 in 20 out of 37 serum samples from individuals classified as deficient.
• Serum from deficient individuals showed increased TCC and decreased C6/C7 after activation.
• Evidence of functionally active terminal complement proteins despite incomplete deficiencies.

Conclusions:

• Sensitive ELISAs can detect C6 and C7 in individuals with complement deficiencies.
• Individuals with C6/C7 deficiencies can still generate TCC, indicating residual protein function.
• Low concentrations of functional C6 and C7 may be sufficient for protection against neisserial infections.