Biotrophs are Specialised (‘obligate’) pathogens

Possess appressoria or haustoria

Narrow host range

Controlled by salicylate-dependent host-defence pathways

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Bacterial Infections

Bacteria enter the body through several natural routes.

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Cell wall endotoxins of some gram-negative bacteria activate macrophages, resulting in release of high levels of IL-1 and TNF-α, which can cause septic shock.

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In staphylococcal food poisoning and toxic shock syndrome, exotoxins produced by the pathogens function as superantigens, which can activate all T cells. 

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Extracellular Bacteria

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Intracellular bacterial

Intracellular bacterial infections tend to induce a cell-mediated immune response, specifically DTH. 

In this response, cytokines secreted by CD4+ T cells are important—most notably IFN-ϒ, which activates macrophages.

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#Id: 9938

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Host immune responses and bacterial evasion mechanisms