An over-reactive immune system affecting the central nervous system, termed multiple sclerosis (MS) hinders especially young adults in their daily life. Demyelination and axonal loss due to neuronal degradation is elicited by auto-reactive inflammatory T-lymphocytes, the main mediators of disease pathogenesis. Many treatment options aim to interfere or block factors involved in this T-cell signaling, but poor oral activity of many target specific drugs is still a severe problem and prompts further investigations. Others, such as fingolimod, dimethyl fumarate and teriflunomide, leading therapy options in MS, often exhibit severe side effects, which limit their long-term therapeutic use. Nature offers a richness of active compounds well applicable as drug candidates. In particular cystine-knot-stabilized circular plant peptides, so-called cyclotides, are ideal tools as novel pharmaceuticals. Cyclotides contain a unique three-dimensional topology and hence exhibit outstanding stability against chemical, thermal and enzymatic deprivation. Furthermore these peptides have publicized a variety of bioactive properties. For instance, kalata B1 (kB1), a prototypical member of the cyclotide family demonstrates hopeful immunosuppressive attributes. kB1 inhibits T-cell autocrine activation and subsequent proliferation by downregulating interleukin-2 cytokine secretion. Therefore the main goal of my thesis was to test and characterize the efficacy of cyclotides in vitro and in an MS model in vivo. After treating mice either parenterally or even orally with the cyclotide [T20K]kB1, exceptional therapeutic effects concerning experimental autoimmune encephalomyelitis pathology could be observed. Cyclotide application led to a better disease status, as well inhibited further relapse of paralysis symptoms. Furthermore, profound adverse effects induced by the plant-derived medication, which were monitored by physiological, biochemical and histological parameters, could be prevented. The impressive activity based on the unique structural feature of cyclotides prompts pharmaceutical drug discovery into a new direction. Plant-derived peptides designates to be a gift from nature for the establishment of new therapeutics against autoimmune, in particular T-cell induced diseases.