Helminth Parasites 1

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*see lecture word document for more notes

Helminth Parasites:

multicellular - contain many different proteins/carbs etc.

complex life cycles - often involving more than one host

Immune responses elicited by helminths:

Th2 dominated

Regulatory T cells

Th2 = IL-4, IL-5 etc.

T helper subsets control disease outcome

Tuft cells produce IL-25 that kick starts the Th2 response

*Schistosome induce dominant Th2 responses

infection elicits a Th1 response

Switches to Th2 co-incident with egg production by adult worms

Th2 responses elicited by eggs are not sufficient to clear worms

Th2 response are involved in pathology of infection,

Th2 responses are essential for host survival

Th2 responses have to be regulated to prevent pathology

*Omega-1 is a glycoprotein released from eggs, and is sufficient to induce strong Th2 responses in absence of IL-4

Schistosome granuloma:

forms around the eggs trapped in tissue

encapsulation of the egg protects hosts from toxins

granuloma is also the cause of disease in humans/mice - hepatic fibrosis

*The Th2 response drives granuloma formation, the cause of liver disease

if no granuloma (IL-4 KO mouse) = death

granuloma is protective but has to be regulated or else liver fibrosis results

liver granulomas decrease in size with chronicity of disease (Th2 responses are modulated)

Need a balance Th1:Th2:Treg response for best outcome