This complexity is highlighted by a study on the CD226 allele, which showed differences between risk and protective alleles in Tregs from healthy controls while Tregs from patients with MS behaved like those from healthy controls with the risk allele, suggesting that protective haplotype effects are nullified in the context of ongoing autoimmune disease.8 It is for this reason that we decided to analyze the impact of the CD226Gly307Ser variant on CD8 T-cell functions in selected PBMCs from 16 donors homozygous for either allele. This evidence concerns the gene CD8A and autoimmune disease.