PRF1 and multiple sclerosis: Interestingly, while classic multiple sclerosis is almostinvariably considered a CD4 T cell mediated disease, it has been notedsince the 1980s that T cells infiltrating the brain of affected individualsare predominantly CD8+.43,44 Similar observationson T cell phenotype have recently been made on brain immune infiltratesin the early stages of Parkinson’s disease.45 However, a pathogenic role for perforin is yet to be provenin either of these diseases.