Relationship between Multiple Sclerosis-Associated IL2RA Risk Allele Variants and Circulating T Cell Phenotypes in Healthy Genotype-Selected Controls

Single nucleotide polymorphisms (SNPs) in or near the IL2RA gene, that encodes the interleukin-2 (IL-2) receptor α (CD25), are associated with increased risk of immune-mediated diseases including multiple sclerosis (MS). We investigated how the MS-associated IL2RA SNPs rs2104286 and rs11256593 are associated with CD25 expression on T cells ex vivo by multiparameter flow cytometry in paired genotype-selected healthy controls. We observed that MS-associated IL2RA SNPs rs2104286 and rs11256593 are associated with expression of CD25 in CD4(+) but not CD8(+) T cells. In CD4(+) T cells, carriers of the risk genotype had a reduced frequency of CD25(+) T(FH)1 cells (p = 0.001) and an increased frequency of CD25(+) recent thymic emigrant cells (p = 0.006). Furthermore, carriers of the risk genotype had a reduced surface expression of CD25 in post-thymic expanded CD4(+) T cells (CD31(−)CD45RA(+)), CD39(+) T(Reg) cells and in several non-follicular memory subsets. Our study found novel associations of MS-associated IL2RA SNPs on expression of CD25 in CD4(+) T cell subsets. Insight into the associations of MS-associated IL2RA SNPs, as these new findings provide, offers a better understanding of CD25 variation in the immune system and can lead to new insights into how MS-associated SNPs contribute to development of MS.