Identification and characterization of a new population of vascular leukocytes. (A) Coexpression of CD45 (labeled with APC-Cy7) and VE-cadherin (labeled with fluorescein isothiocyanate [FITC]) defines a new population of tumor-infiltrating host cells. These are highly frequent in all solid human ovarian carcinoma specimens analyzed but are rare in tumor ascites (top, right) or peripheral blood from tumor-bearing patients (bottom, right). (B) Phenotypic discrimination between VLCs and classical endothelial cells. Results are representative of at least 3 different tumors analyzed for each marker. The y-axis shows antigen-presenting cell (APC)–labeled antibodies; the x-axis, phycoerythrin (PE)–labeled antibodies. A compensation control is also shown. (C) Side scatter (FSC and SSC) characteristics of the 3 main populations found in mechanically dissociated ovarian tumor specimens. (D) Real-time RT-PCR analysis of different leukocyte and endothelial makers in ECs, VLCs, HUVECs, and normal human spleen. Error bars indicate standard deviation.