Intravital imaging of T cell priming in the gut-associated lymphatic tissue (GALT)

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Multiple sclerosis (MS), a common autoimmune disease, is characterized by infiltration of immune cells into the central nervous system (CNS). In my previous work I showed by intravital imaging that the infiltration and activation of autoreactive CD4 positive T cells in the CNS is critical for the initiation of CNS inflammation. However, it is still largely unknown why encephalitogenic T cells start infiltration into the CNS. Although these cells exist normally in healthy immune repertoire, they only start infiltrating into the CNS and induce local inflammatory lesions if triggered to do. Since it was shown that gut microbiota can trigger the onset of experimental autoimmune encephalomyelitis (EAE), an animal model of MS, I hypothesize that the encephalitogenic T cells get primed for CNS infiltration in the gut. To directly test this hypothesis, I have established an intravital imaging that allows to visualize by two-photon microscopy when and where T cells are stimulated in the gut-associated lymphatic tissue (GALT). To do so I will express two activation sensors that I have previously developed in encephalitogenic T cells. Whereas the calcium sensing protein, Twitch, detects changes of the intracellular calcium level that allow a graded assessment of T cell stimulation, the nuclear translocation of the NFAT-GFP fusion protein selectively detects antigen-dependent T cell activation, which is only induced by saturated calcium signaling. To study the consequences of T cell priming in the GALT, the GALT-emigrating cells will be recovered from efferent lymphatics and their phenotype will be analyzed by next-generation sequencing (NGS). Based on the molecular profiling of the GALT-emigrating cells I will define "encephalitogenic switches that can be therapeutically targeted to prevent the subsequent induction of CNS inflammation.