Effects of PF4 on the surface expression of different monocyte markers.

Immunofluorescence-staining of human monocytes with antibodies directed against carboxypeptidase (A) M/MAX1, (B) HLA-DR, (C) CD14, (D) CD80, or (E) CD86 was performed either with freshly isolated cells (left column) or with cells cultured for 72 hours in the absence (middle column) or presence (right column) of 4 μmol/L PF4. Cells were analyzed for the respective surface marker expression (gray histograms) or isotype controls (open histograms) by flow cytometry. Percentage values refer to the relative number of positive cells and values within brackets to mean fluorescence intensity of these cells. Data are derived from 1 representative experiment out of at least 6. Significant differences between numbers of positive cells from PF4-treated and untreated cells after culture were observed in panel A (n = 10,P < .006), panel B (n = 9, P < .008), panel C (n = 9, P < .005), and panel E (n = 11,P < .006).