The central EBNA1 epitope marginalized in MS (amino acids FENIAEGLRALLARSHVER) could well have different functions in health and in MS and is therefore a major putative candidate for generation of T reg s which control the relevant immune processes. A specific or functional deficiency of T reg s in MS has only recently been recognised, and the need for a large cohort of T reg s for the resolution of experimental autoimmune encephalomyelitis has been demonstrated [44] . For the purpose of studying the potential infectious and immunological background of MS, it is relevant to search for homologies to this 'epitope No. 1' in the MS-associated pathogens [42, 43] . Interestingly, homologies to the putative epitope were found in all these pathogens (Table 3) .