The vesiculation process. Three enzymes are responsible for membrane asymmetry. Upon activation by agonists, Ca2+ is mobilised from the endoplasmic reticulum and the Golgi apparatus, intracellular calcium concentration rises and activates calpain as well as other decoupling enzymes. Cytoskeleton anchoring to plasma membrane is disrupted. At the same time, membrane polarity is inversed, membrane blebs are allowed to form and are released in the extracellular space. Microparticles (MP) keep their inverted polarity conformation and bear surface antigens from their cell of origin.
Coltel N, Combes V, Wassmer SC, Chimini G, Grau GE. Cell vesiculation and immuno-pathology: implications in cerebral malaria. Microbes Infect. 2006 8(8):2305-16. PMID: 16829152