In the last two decades, Th17 CD4+ T cells have emergedas a major pathogenic cells in autoimmune diseases.[48–51] As discussed above, microbiota play a criticalrole in the generation of these Th17 cells.[42,83,84]Importance of gut microbiota in the generation of Th17 cells can behighlighted by the fact that there is absence or severely reduced levels ofIL-17 in GF mice.[42]Animal models of human mono/poly-genic autoimmune disorders are influencedby microbiota. Here, CD4 is linked to autoimmune disease.