Helminth exposure selects for a protective Th2 immune response that simultaneously increases risk for fibrosis.

<p>The high prevalence of helminths in Africa has selected for genotypes favoring an enhanced Th2 immune response characterized by increased levels of interleukin 4 (IL4), interleukin 13 (IL13), and interleukin 4 receptor (IL4R), and other Th2 factors. This selection also decreases Th1 factors, such as interferon gamma (IFNG) and interferon gamma receptor (IFNGR), and Th2 regulatory factors, such as IL10 and interleukin 13 receptor alpha 2 (IL13RA2). These genotypes increase resistance to helminthic infection and contribute to a subset of fibroproliferative diseases that are more common and/or more severe in individuals of African ancestry. Global distribution of helminth species in upper part of figure adapted from Lustigman et al. [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1005568#pgen.1005568.ref168" target="_blank">168</a>].