Abstract
Many diseases are differentially distributed among human populations. Differential selection on genetic variants in ancestral environments that coincidentally predispose to disease can be an underlying cause of these unequal prevalence patterns. Selected genes may be pleiotropic, affecting multiple phenotypes and resulting in more than one disease or trait. Patterns of pleiotropy may be helpful in understanding the underlying causes of an array of conditions in a population. For example, several fibroproliferative diseases are more prevalent and severe in populations of sub-Saharan ancestry. We propose that this disparity is due to selection for an enhanced Th2 response that confers resistance to helminthic infections, and concurrently increases susceptibility to fibrosis due to the profibrotic action of Th2 cytokines. Many studies on selection of Th2-related genes for host resistance to helminths have been reported, but the pleiotropic impact of this selection on the distribution of fibrotic disorders has not been explicitly investigated. We discuss the disproportionate occurrence of fibroproliferative diseases in individuals of African ancestry and provide evidence that adaptation of the immune system has shaped the genetic structure of these human populations in ways that alter the distribution of multiple fibroproliferative diseases.
Highlights
We propose that the increased prevalence of fibroproliferative diseases in individuals of African ancestry is due to selective pressure for an elevated Th2 response that confers resistance to helminthic infections and concomitantly increases susceptibility to fibrosis
Patients with progressive systemic sclerosis exhibit a predominant type 2 response, which accounts for the endothelial cell injury, fibrosis, and autoantibody production in this disease [55,56]
Mutations in IL13Rα2, a decoy receptor that serves as an off-signal for IL13 [57,58], are associated with systemic sclerosis [59]
Summary
Editor: Ernst J Reichenberger, University of Connecticut Health Center, UNITED STATES. Differential selection on genetic variants in ancestral environments that coincidentally predispose to disease can be an underlying cause of these unequal prevalence patterns. Several fibroproliferative diseases are more prevalent and severe in populations of sub-Saharan ancestry. We propose that this disparity is due to selection for an enhanced Th2 response that confers resistance to helminthic infections, and concurrently increases susceptibility to fibrosis due to the profibrotic action of Th2 cytokines.
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