Some bacteria produce molecules called invasins that activate the host cell's cytoskeletal machinery enabling bacterial entry into the cell by phagocytosis. By entering the cytoplasm of the host cell, it has a ready supply of nutrients and is able to protect the bacteria from complement, antibodies, and certain other body defenses. Many bacteria use injectisomes, such as a type 3 secretion system, to inject effector molecules into the host cell's cytoplasm.