We have classified microvesicles into two subtypes: larger MVs released upon stimulation of prostate cancer cells, sMVs, and smaller cMVs, released constitutively. cMVs are released as part of cell metabolism and sMVs, released at 10-fold higher levels, produced upon activation, including sublytic C5b-9. From electron microscopy, nanosight tracking analysis, dynamic light scattering and flow cytometry, cMVs (194-210 nm in diameter) are smaller than sMVs (333-385 nm). Furthermore, using a Quartz Crystal Microbalance measuring changes in resonant frequency (Delta f) that equate to mass deposited on a sensor, an sMV and a cMV are estimated at 0.267 and 0.241 pg, respectively. sMVs carry more calcium and protein, express higher levels of lipid rafts, GPI-anchored CD55 and phosphatidylserine including deposited C5b-9 compared to cMVs. This may allude to biological differences such as increased bound C4BP on sMVs inhibiting complement more effectively. (C) 2015 Elsevier Inc. All rights reserved.