A quantitative method for measuring innate phagocytosis by human monocytes using real-time flow cytometry

Area of Science:

• Immunology
• Cell Biology
• Biotechnology

Background:

• Phagocytosis is a critical immune process.
• Existing methods for quantitative phagocytosis assessment lack speed and standardization.
• A need exists for a reliable assay to measure monocyte phagocytic capacity.

Purpose of the Study:

• To develop and validate a real-time flow cytometric method for quantifying phagocytosis.
• To assess the influence of various experimental conditions on phagocytic rates.
• To evaluate the method's applicability for routine clinical use and simultaneous calcium measurement.

Main Methods:

• Real-time flow cytometry was used to measure the uptake of fluorescent latex beads by human monocytes.
• Experiments were conducted under serum-free conditions, optimizing buffer composition, temperature, and pH.
• A simplified whole blood method was developed for clinical applications.

Main Results:

• The developed flow cytometry method accurately quantifies phagocytosis in real-time.
• Phagocytic rates were influenced by buffer composition, temperature, and bead surface properties.
• Monocyte phagocytic ability showed inter-individual variation but was stable over time within individuals.
• The simplified method yielded comparable results to the optimized assay.
• The method allows simultaneous measurement of cytosolic calcium levels during phagocytosis.

Conclusions:

• A rapid, standardized, and reproducible flow cytometric assay for quantitative phagocytosis assessment has been established.
• This method is suitable for both research and routine clinical applications, offering insights into immune cell function.
• The assay provides a valuable tool for studying phagocytosis and associated cellular signaling pathways.