Polymorphonuclear leukocyte chemotaxis in systemic lupus erythematosus

Area of Science:

• Immunology
• Biochemistry

Background:

• Human serum contains a polypeptide (cochemotaxin) that enhances C5a desarg chemotactic activity.
• C5a desarg is a complement fragment involved in immune responses.

Purpose of the Study:

• To investigate the role of cochemotaxin in amplifying C5a desarg's chemotactic activity.
• To identify the components responsible for chemotactic activity in human serum.

Main Methods:

• Analysis of human serum components.
• Assays to measure chemotactic activity of polymorphonuclear leukocytes.

Main Results:

• A specific anionic polypeptide (cochemotaxin) was identified in normal human serum.
• Cochemotaxin permits low concentrations of C5a desarg to be chemotactically active for human polymorphonuclear leukocytes.
• The complex of C5a desarg and cochemotaxin accounts for most of the chemotactic activity generated in human serum.

Conclusions:

• Cochemotaxin plays a significant physiologic role in amplifying C5a desarg's chemotactic activity, especially under limited complement activation.
• The C5a desarg-cochemotaxin complex is likely the target of the Bb fragment of Factor B in patients with systemic lupus erythematosus.