An important component of the innate immune system evolved differently in different human populations, depending on the infectious diseases that each population has encountered, suggests a study published online this week in the Proceedings of the National Academy of Sciences. The authors found that variants of an immune receptor protect against bacterial infection in Europeans and Asians, while Africans often possess a version of the receptor that protects against malaria."Our study demonstrates that during migration out of Africa, the immune system has been changed by the infections it has encountered," senior author Mihai Netea of Radboud University Nijmegen Medical Center in the Netherlands told The Scientist in an Email.Toll-like receptors (TLRs) defend hosts by recognizing molecules that all pathogens possess. One of these receptors, TLR4, protects against Gram-negative bacteria, mycobacteria, fungi, and malaria parasites.Previous work has identified two common single nucleotide polymorphisms (SNPs) in TLR4...

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