Circulating immune complexes in Crohn's disease. Their characterization and interrelationship with components of the...

Area of Science:

• Immunology
• Gastroenterology
• Clinical Chemistry

Background:

• Crohn's disease (CD) is a chronic inflammatory bowel disease.
• The complement system plays a crucial role in immune responses and inflammation.
• Dysregulation of the complement system has been implicated in various autoimmune and inflammatory conditions.

Purpose of the Study:

• To investigate the evidence of complement system activation in patients with Crohn's disease.
• To explore the potential role of anticomplementary activity and immune complexes in CD pathogenesis.

Main Methods:

• Analysis of sera from Crohn's disease patients for anticomplementary activity.
• Measurement of complement components C3 and C4 levels.
• Detection of C3 inactivation products in serum and plasma.
• Gel filtration chromatography to characterize anticomplementary activity and identify associated immunoglobulins.

Main Results:

• 37% of Crohn's disease patients' sera showed anticomplementary activity.
• Significantly increased C3 and C4 levels were observed in CD patients compared to controls.
• C3 inactivation products were detected in 32.9% of CD patient samples, indicating in vivo complement activation.
• Anticomplementary activity correlated with C3 activation and was associated with high molecular weight fractions containing IgG and IgA, suggesting immune complex formation.

Conclusions:

• The complement system is activated in a subset of patients with Crohn's disease.
• Anticomplementary activity in CD sera is likely mediated by circulating immune complexes.
• These findings suggest that complement activation via immune complexes may contribute to the pathogenesis of Crohn's disease.