**2.3 "Trigger" phagocytosis**

In contrast to zipper phagocytosis, the "trigger mechanism" is a process where engagement of the pathogen with a pathogen recognition receptor is not a critical component of the process. Some engagement with cell surface ligands may occur to secure the pathogen to the cell [80]; however, the distinguishable difference in trigger phagocytosis is that the pathogen "injects" effectors into the host cell. The injected components known as type-III (T3SS) [85] and type-IV (T4SS) [86] secretion systems result in host cell cytoskeletal rearrangements localized to the site of pathogen contact. Rearrangement generates "ruffles" along the cell surface, which then fold over the pathogen and fuse, internalizing the pathogen (**Figure 2**) [80].
