GrB distribution and cytotoxic potential of CD8+ T cells was confirmed using z-stack confocal laser microscopy on 12 WML biopsies of 10 additional MS patients assayed by triple immunofluorescence staining for CD8, grB and the early apoptotic marker “cleaved caspase 3” (cCASP3). This evidence concerns the gene GZMB and myeloid sarcoma.