No difference in blood Foxp3+ Treg frequency and intracellular production of IFNγ, IL-17, IL-4, and IL-10 by CD4+ T cells. IL-17+ T cells correlated with gut microbiota richness in MS patients. IL-17+ T cells inversely correlated with Bacteroidetes abundance in patients. Treg frequency correlated with Fusobacteria abundance in healthy controls. Here, IFNG is linked to myeloid sarcoma.