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Updated: Jan 10, 2026
Disorders of Erythrocytes
Defective release of C5a related chemo-attractant activity from complement in Crohn's disease
Insights
Crohn's disease patients show impaired alternative pathway complement activation, affecting neutrophil function. This suggests a role for gut bacteria in Crohn's pathogenesis and inflammation.
Area of Science:
- Immunology
- Gastroenterology
Background:
- Crohn's disease is a chronic inflammatory condition of the gastrointestinal tract.
- The complement system plays a crucial role in immune responses.
- Dysregulation of the complement system may contribute to Crohn's disease pathogenesis.
Purpose of the Study:
- To investigate complement system activation in untreated Crohn's disease patients.
- To assess the function of the alternative complement pathway in Crohn's disease.
Main Methods:
- Studied 20 untreated Crohn's disease patients and 20 healthy volunteers.
- In vitro activation of the complement cascade reaction.
- Measured total hemolytic complement, C5a chemo-attractant activity, and C3 utilization.
Main Results:
- Total hemolytic complement levels were normal in all patients.
- Activation of the alternative pathway showed decreased C5a release and subnormal C3 utilization.
- Complement abnormalities were not linked to disease activity, site, or duration.
Conclusions:
- Inadequate stimulation of neutrophil functions may occur due to bacterial components activating the alternative pathway in Crohn's disease.
- Delayed clearance of foreign material from the gut mucosa could contribute to granulomatous inflammation via a foreign body reaction.
Abstract:
Complement was studied in 20 untreated cases of Crohn's disease and in 20 healthy volunteers by an in vitro activation of the cascade reaction. Total haemolytic complement was normal in all patients. In contrast, activation of the alternative pathway lead to a decreased release of C5a related chemo-attractant activity together with a subnormal utilisation of the main complement component C3. This abnormality of complement function was not related to the activity of the disease, site of involvement or to disease duration. The results suggest that an inadequate stimulation of important neutrophil functions may result when bacterial lipopolysaccharides and other macromolecules activating the alternative pathway penetrate the gut mucosa. A delayed clearance from the tissue of such foreign material could be a further pathogenic factor in Crohn's disease leading to granulomatous inflammation by a foreign body reaction.
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