Four-color flow cytometry evaluation of circulating endothelial cells and endothelial progenitors.

(A) Representative panel (left) shows the analysis gate used to exclude platelets, death cells, and debris and the reference beads used to obtain absolute cell count. The other panel (right) shows the gate used to exclude hematopoietic cells expressing the CD45 antigen. (B,C) Middle and bottom panels indicate negative controls and the expression of antigens used to evaluate resting (CD31 and CD34), activated (CD105 and CD106), and progenitor (CD133) endothelial cells. (B) Middle panels show the resting phenotype of a representative healthy control; (C) bottom panels show the more activated phenotype of a representative newly diagnosed BC patient. R4 indicates CD45-hematopoietic progenitors depicted by high CD34 expression.