Figure 4. β₂GPI is detectable on the neutrophil surface.

A, Neutrophils and peripheral blood mononuclear cells (PBMCs) were isolated from healthy controls. Total protein extracts were prepared by detergent lysis. Western blotting was to β₂GPI, annexin A2, and β-actin. Quantification was by densitometry and is expressed in arbitrary units. Bars represent mean and SEM. N=6, including 3 samples for each group not pictured here; western blotting was repeated twice with similar results. ***p<0.001. B, Neutrophils were isolated from healthy controls and allowed to adhere to coverslips. Cells were then immediately fixed with paraformaldehyde, and in some cases permeabilized with detergent (0.1% Triton). Representative images are shown with β₂GPI and neutrophil elastase stained green and DNA stained blue. Scale bars=25 microns. C, Neutrophils and monocytes were identified by forward/side-scatter, and additionally confirmed to be CD10-positive and CD14-positive, respectively. The percentage of β₂GPI-positive cells was then determined. Bars represent mean and SEM. N=6 healthy controls for each group; **p<0.01. To the right is a representative neutrophil histogram, demonstrating that the majority of CD10-positive cells are also positive for β₂GPI.