Chemotactic factor inactivators of human granulocytes

Area of Science:

• Immunology
• Biochemistry

Background:

• Neutrophils release substances during phagocytosis, including chemotactic factor activators and inactivators.
• These substances are generally considered hydrolytic enzymes, with elastase and cathepsin G being major proteases from lysosomal granules.

Purpose of the Study:

• To investigate the role of granule elastase and cathepsin G as inactivators of chemotactic factors released by neutrophils during phagocytosis.

Main Methods:

• Purification of elastase and cathepsin G from human neutrophils using Trasylol-Sepharose and CM-cellulose chromatography.
• Assessing the inactivator activity of purified enzymes and neutrophil supernatant fluids against C5, C3, and bacterial chemotactic factors.

Main Results:

• Purified elastase and cathepsin G (approx. 3 µg) completely inactivated C5 chemotactic factor generated in human serum.
• Higher concentrations were required for C3 chemotactic factor inactivation, and these enzymes were largely ineffective against bacterial chemotactic factors.
• Neutrophil supernatant fluids showed inactivator activity for both C5 and bacterial factors; elastase inhibition primarily affected C5 factor inactivation.

Conclusions:

• Neutrophil-released elastase and cathepsin G exhibit specific inactivator activity towards chemotactic factors.
• The predominant inactivator of the C5 chemotactic fragment is attributable to elastase and cathepsin G.
• There is heterogeneity in chemotactic factor inactivator activity released by phagocytosing neutrophils.