CAP37, a human neutrophil-derived chemotactic factor with monocyte specific activity

Area of Science:

• Immunology
• Biochemistry

Background:

• CAP37 is an antimicrobial protein found in human neutrophil granules.
• It plays a role in inflammatory processes.

Purpose of the Study:

• To investigate the chemotactic properties of CAP37 for different immune cells.
• To explore the potential role of CAP37 in inflammatory responses.

Main Methods:

• Purification of CAP37 using sequential chromatography (carboxymethyl Sephadex, G-75 Sephadex, hydrophobic interaction HPLC).
• Chemotaxis assays using human and rabbit mononuclear cells, neutrophils, and lymphocytes.
• Sequence analysis of the N-terminus of CAP37.
• Inhibition assays using diisopropyl fluorophosphate.
• Observation of CAP37 release during Staphylococcus aureus phagocytosis by neutrophils.

Main Results:

• Purified CAP37 is a potent chemoattractant for human monocytes at nanomolar concentrations, comparable to formyl-methionyl-leucyl-phenylalanine.
• CAP37 lacks chemotactic activity for neutrophils and lymphocytes but shows chemokinetic effects.
• CAP37 is also chemotactic for rabbit mononuclear cells, requiring higher concentrations.
• Sequence analysis suggests CAP37 lacks serine protease activity.
• Significant extracellular release of CAP37 from neutrophils occurs during Staphylococcus aureus phagocytosis.

Conclusions:

• CAP37 acts as a specific chemoattractant for monocytes.
• Neutrophil-derived CAP37 released during phagocytosis may orchestrate monocyte recruitment in inflammatory responses.