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More than one third of the world’s population is infected with the tubercle bacteria, Mycobacterium tuberculosis, but only a small proportion of them fall sick. Little is known about the protective factors. Twin studies have shown, however, that the genetic make-up plays a pivotal role. In a Ghanaian population, we have extensively studied the genes coding for proteins, which recognise infectious agents on the surface of immune cells.
By comparing thousands of tuberculosis (TB) patients with non-affected per-sons, we found that a mutation changing the structure of the recognition molecule TLR1, provides an outstandingly strong protection of 80% against TB. Apparently, this variant of the receptor recognises TB bacteria exceedingly well and stimulates protective immune responses. It is, however, very exclusive. In its protective (homozygous) form, it occurs in no more than 0.6% of the Ghanaians studied and 0.1% of Europeans. Presumably it has either arisen only a few generations ago or is beset with serious disadvantages, otherwise evolution would have spread the mutation more widely.
Christian Meyer, Christa Ehmen, Gerd Ruge, Rolf Horstmann, Thorsten Thye and external cooperation partners (see publication)