Our finding, that IL-17A mediates only modest CNS effects whereas severe detrimental effects for this cytokine have clearly been demonstrated for several peripheral organs has also been described for other cytokines as well: e.g. CCL21, which mediates chemotaxis of lymphocytes, induces thyroiditis if expressed under the promotor for thyroglobulin [77] whereas the expression of bioactive CCL21 under the GFAP promoter neither induced lymphocytic infiltration nor glial activation [78]. Here, CCL21 is linked to thyroiditis.