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Related Experiment Video

Updated: Jul 15, 2026

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells

Published on: January 29, 2014

Complement 1 inhibitor is a regulator of the alternative complement pathway.

H Jiang¹, E Wagner, H Zhang

¹Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.

The Journal of Experimental Medicine

|December 6, 2001

Summary

Complement 1 inhibitor (C1-INH) regulates the alternative complement pathway. This study shows C1-INH inhibits paroxysmal nocturnal hemoglobinuria (PNH) erythrocyte lysis by preventing factor B and C3 binding.

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Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells

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Measuring Erythrocyte Complement Receptor 1 Using Flow Cytometry

Measuring Erythrocyte Complement Receptor 1 Using Flow Cytometry

Published on: May 19, 2020

Area of Science:

Immunology
Complement System Biology

Background:

The alternative complement pathway is a crucial part of innate immunity.
Dysregulation of the alternative pathway is implicated in various diseases.
Complement 1 inhibitor (C1-INH) is a known regulator of the classical and lectin pathways.

Purpose of the Study:

To investigate the role of C1-INH as an inhibitor of the alternative complement pathway.
To elucidate the molecular mechanisms by which C1-INH regulates the alternative pathway.

Main Methods:

Assessing C1-INH's effect on paroxysmal nocturnal hemoglobinuria (PNH) erythrocyte lysis in human serum.
Measuring the binding of factors B and C3 to erythrocytes.
Investigating C1-INH interaction with C3b and cobra venom factor (CVF) using immobilized assays.
Analyzing the effect of C1-INH on factor D-mediated cleavage of factor B.
Evaluating alternative pathway lysis upon C1-INH removal from serum.

Main Results:

C1-INH prevented alternative pathway-induced lysis of PNH erythrocytes.
C1-INH inhibited the binding of factors B and C3 to erythrocytes.
C1-INH bound to C3b and CVF, preventing factor B interaction with these components.
C1-INH inhibited factor D-mediated cleavage of factor B and subsequent C3 cleavage.
Removal of C1-INH significantly increased alternative pathway lysis.

Conclusions:

C1-INH acts as a physiological downregulator of the alternative complement pathway convertase.
C1-INH inhibits the alternative pathway by interfering with factor B binding to C3b.
These findings highlight C1-INH's potential therapeutic role in alternative pathway-mediated diseases.