An excerpt from the description of the study: ''The main goal of this study is to determine changes in the epigenetic regulation in each of the six main subtypes of immune cells caused by ME/CFS: helper T cells, cytotoxic T cells, B cells, NK cells, dendritic cells and monocytes in order to determine, how each cell population is affected by the disease. This study will provide further insight into mechanisms of ME/CFS onset, activity and progression as well as specific cell to cell variation in the immune system. We will also identify novel pathways specific for the cell subtypes that can be used to target diagnosis and treatment more effectively, addressing the underlying cause of disease.''