Isolation of circulating human monocytes with high purity for proteomic analysis

Area of Science:

• Immunology
• Proteomics
• Cell Biology

Background:

• Monocyte isolation is crucial for proteomic analysis.
• Previous methods often result in contamination, affecting results.
• High purity is essential for accurate proteomic studies.

Purpose of the Study:

• To develop a simple, rapid, and high-purity method for isolating human blood monocytes for proteomic analysis.
• To ensure the isolated monocytes are free from common contaminants like platelets, lymphocytes, albumin, and immunoglobulins.
• To enable reproducible protein analysis from monocytes for clinical studies.

Main Methods:

• Monocytes were purified using gradient centrifugation and positive selection with monoclonal antibodies and paramagnetic beads.
• Elution conditions were optimized to minimize albumin contamination.
• Purity was assessed using flow cytometry, and protein analysis was performed via two-dimensional gel electrophoresis (2-DE) after DNAse treatment.

Main Results:

• The method routinely yields 10^7 monocytes with >96% purity from 28 mL of blood.
• Recovered protein yield ranged from 200-250 microg per isolation.
• 2-DE analysis detected over 1500 spots in the 4-7 pH range and >2000 spots in total, with DNA identified as a key contaminant removed by DNAse.

Conclusions:

• This optimized method provides a rapid (3-hour) and reproducible means for high-purity monocyte isolation for proteomic studies.
• The technique is suitable for large-scale clinical investigations, enabling comparative analyses of normal and pathological samples.
• It facilitates longitudinal studies by allowing follow-up of monocyte protein expression in individual patients.