Another study by Hedström and colleagues included in our review provided data on the interaction between the HLA-DRB1 * 15 and HLA-A * 02 genotypes – the former being associated with an increased risk of MS and the latter having a protective effect for MS.22As in their previous study, confounding factors, such as vitamin D and Epstein Barr virus status, were analyzed and the selection of subjects was restricted to people who never smoked. Here, HLA-A is linked to myeloid sarcoma.