This Newsweek title neatly sums up findings from the recent high-impact Nature paper on the ancient origins of Multiple Sclerosis genetics. Plus, an alternate hypothesis for how this immune gene correlates with the emergence of MS would be as follows…Immunological protection against certain sheep & cattle pathogens leads to personal behaviors and cultural practices that increase exposures to these animals and to their dairy products. These increased windows of exposure open the door for other sheep-related pathogens, i.e., epsilon neurotoxin-C. perfringens bacteria (which the gene likely fails to protect against) to then take root in the exposed population and brain lesions ensue.
In the primary research article (see link below), Barrie et al. also identified the LCT/MCM6 gene, which allows adults to consume milk into adulthood, as emerging in their ancestral genomic dataset alongside the immune gene HLA-DRB1* 15:01. This to me is the real story! Sure, the HLA gene may have protected ancient European sheep herders from dying from animal pathogens, but evolving to become lactose tolerant is what I think predisposes Northern Europeans to MS in the present day. This would also explain the MS latitude gradient, as populations inhabiting equatorial regions are by-and-large lactose intolerant and will naturally avoid exposure to ETX-encoding C. perfringens strains.
In the primary research article (see link below), Barrie et al. also identified the LCT/MCM6 gene, which allows adults to consume milk into adulthood, as emerging in their ancestral genomic dataset alongside the immune gene HLA-DRB1* 15:01. This to me is the real story! Sure, the HLA gene may have protected ancient European sheep herders from dying from animal pathogens, but evolving to become lactose tolerant is what I think predisposes Northern Europeans to MS in the present day. This would also explain the MS latitude gradient, as populations inhabiting equatorial regions are by-and-large lactose intolerant and will naturally avoid exposure to ETX-encoding C. perfringens strains.
https://www.nature.com/articles/s41586-023-06618-z