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. 2011 May;7(5):e1002003.
doi: 10.1371/journal.ppat.1002003. Epub 2011 May 12.

Evolution of Th2 immunity: a rapid repair response to tissue destructive pathogens

Judith E Allen  1 , Thomas A Wynn
Affiliations

Evolution of Th2 immunity: a rapid repair response to tissue destructive pathogens

Judith E Allen et al. PLoS Pathog. 2011 May.
No abstract available

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Helminths induce extensive tissue damage, providing evolutionary pressure for an adaptive Th2-mediated wound healing response.
In this example, a human infected with the helminth parasite S. mansoni is faced with constant tissue damage as the parasite completes its life cycle. (A) Infectious cercariae are released from the intermediate snail host and are attracted to lipids found on human skin. Once attached to the skin, they often enter through hair follicles where they secrete proteases, degrade basement membranes, and ultimately gain access to the vasculature. (B) Immature schistosomula are then swept up in the heart and lodge in the lungs, where they must cross capillary beds to enter the arterial flow. (C) Eventually, adult parasites find their way to the mesenteric veins, where they mate and begin laying eggs. Many of the eggs migrate from the vasculature, enter the wall of the intestine and literally burrow through until they reach the lumen and are excreted in the feces. (D) A subset of eggs is swept by the blood flow into the liver where they are trapped in the small sinusoidal vessels, inducing a vigorous granulomatous response. Thus, at nearly all stages of the parasite's life cycle, it is inducing significant tissue damage and hemorrhaging in the definitive host. It is imperative that “holes” in important barriers are repaired quickly; otherwise, bacteria would quickly invade and take over.
See this image and copyright information in PMC

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