What causes relapses of autoimmune diseases? The etiological role of autoreactive T cells

Most human autoimmune diseases have a relapsing remitting or a chronic progressive course, while animal models are usually acute and monophasic. In our experimental animal model the disease can be either monophasic or remitting, depending on the autoantigen used for induction, and it appears to lie in the effector phenotype of the elicited T helper cell response. Since both, monophasic and relapsing courses of disease are induced by immunization as well as by adoptive transfer of peptide-specific, CD4(+) T cells, we were able to directly compare the transcriptomes of pathogenic T cell lines by gene array analysis and qPCR as well as protein expression. Upregulated genes were only determined in T cells inducing relapsing uveitis and belong to certain pathways of antigen presentation, activation, inflammation, migration and survival, comprising WNT, Hedgehog, MAP-kinase and JAK/STAT-pathways. These pathways are partially interacting with each other, and the central molecule upregulated in T cells causing relapsing disease was found to be IFN-gamma. Here the course of the autoimmune diseases strictly depends on the characteristics of the autoreactive T cells, which are already determined at their early stage of antigen-specific activation. Our rat models of experimental autoimmune uveitis could help elucidating the immune mechanisms behind relapsing autoimmunity in order to develop better therapeutic strategies. (C) 2013 Elsevier B.V. All rights reserved.