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## Intracellular mechanism of infection In order to avoid destruction by the immune system and thrive, the *Leishmania* 'hides' inside its host's cells. This location enables it to avoid the action of the humor immune response (because the pathogen is safely inside the cell and outside the open blo...

## Intracellular mechanism of infection In order to avoid destruction by the immune system and thrive, the *Leishmania* 'hides' inside its host's cells. This location enables it to avoid the action of the humor immune response (because the pathogen is safely inside the cell and outside the open bloodstream), and furthermore may prevent the immune system from destroying its host through nondanger surface signals which discourage apoptosis. The primary cell types *Leishmania* inf ltrates are phagocytotic cells such as neutrophils and macrophages. Usually, a phagocytotic immune cell like a macrophage will ingest a pathogen within an enclosed endosome and then fill this endosome with enzymes which digest the pathogen. However, in the case of *Leishmania*, these enzymes have no effect, allowing the parasite to multiply rapidly. This uninhibited growth of parasites eventually overwhelms the host macrophage or other immune cell, causing it to die. *Leishmania* possesses a lipophosphoglycan coat over the outside of the cell. Lipophosphoglycan is a trigger for toll-like receptor 2, a signalling receptor involved in triggering an innate immune response in mammals. Lectins, a group of proteins which bind different glycans, are often used to detect these lipophosphoglycan variants. Lipophosphoglycan is used by the parasite to promote its survival in the host and the mechanisms by which the parasite does this center around modulating the immune response of the host. This is vital, as the *Leishmania* parasites live within macrophages and need to prevent the macrophages from killing them. Lipophosphoglycan has a role in resisting the complement system, inhibiting the oxidative burst response, inducing an inflammation response and preventing natural killer T cells recognizing that the macrophage is infected with the *Leishmania* parasite.