Granulocyte aggregometry: a sensitive technique for the detection of C5a and complement activation

Area of Science:

• Immunology
• Complement System
• Cellular Immunology

Background:

• Complement (C) activated plasma induces granulocyte (polymorphonuclear neutrophil - PMN) aggregation.
• C5a is the specific mediator responsible for C-induced PMN aggregation.
• Cytochalasin-B (CB) treatment enhances and irreversibly activates C-induced PMN aggregation.

Purpose of the Study:

• To evaluate granulocyte aggregometry as a sensitive method for detecting C-activation.
• To compare the sensitivity of granulocyte aggregometry with standard C-activation detection methods.
• To assess the utility of granulocyte aggregometry in detecting in vivo C-activation.

Main Methods:

• Graded C-activation was induced in vitro by treating fresh serum with varying concentrations of zymosan.
• PMN aggregation was measured using granulocyte aggregometry in response to C-activated plasma.
• C3 immunoelectrophoresis was used as a comparative standard for C-activation detection.

Main Results:

• Granulocyte aggregometry demonstrated superior sensitivity in detecting C-activation compared to C3 immunoelectrophoresis.
• Aggregometry detected C-activation induced by 0.02 mg zymosan/ml serum, which was 10-fold lower than required for C3 immunoelectrophoresis.
• Aggregating activity was detected in plasmas from patients with systemic lupus erythematosus, immune vasculitis, and transfusion reactions, indicating in vivo C-activation.

Conclusions:

• Granulocyte aggregometry is a highly sensitive technique for detecting both in vitro and in vivo complement activation.
• The magnitude of PMN aggregation is proportional to the concentration of activated plasma, enabling quantitative assessment.
• This method holds potential for diagnosing and monitoring conditions associated with aberrant complement system activity.