activation by specific cargoes, including growth factors, ligands of integrins, and apoptotic cell remnants. These ligands activate a complex signaling pathway, resulting in a change in actin dynamics and the formation of cell-surface protrusions of filopodia and lamellopodia, commonly called ruffles. When ruffles collapse back onto the membrane, large fluid-filled endocytic vesicles form called macropinosomes, which can transiently increase the bulk fluid uptake of a cell by up to tenfold. Macropinocytosis is a solely degradative pathway: macropinosomes acidify and then fuse with late endosomes or endolysosomes, without recycling their cargo back to the plasma membrane. Some bacteria and viruses have evolved to induce macropinocytosis as a mechanism for entering host cells. Some of these can stop the degradation processes in order to survive inside the macropinosome, which may transform into smaller and long-lasting vacuoles containing the viruses or bacteria (some of which may replicate inside), or simply escape through the wall of the macropinosome when inside. For example, the gut pathogen Salmonella typhimurium injects toxins into the host cell in order to induce macropinocytosis as a form of uptake, inhibits the degradation of the macropinosome, and forms a salmonella-containing vacuole, or SCV, wherein it can replicate. See also Phagocytosis Receptor-mediated endocytosis Caveolae References Campbell, Reece, Mitchell: "Biology", Sixth Edition, Copyright 2002 P. 151 Marshall, Ben, Incredible Biological Advancements of the 20th Century, Copyright 2001 p. 899 Alrt, Pablo, Global Society Harvard study, copyright 2003 p. 189 Brooker, Robert: "Biology", Second Edition, Copyright 2011 p. 116 Cherrr, Malik, The Only Edition, Copyright 2012, p. 256 Abbas, Abul, et al. "Basic Immunology: Functions and Disorders of the Immune System." 5th ed. Elsevier, 2016. p. 69 Cellular processes