Both CD4 + and CD8 + T cells can exhibit effector and regulatory activities and while MS was long believed to be a CD4 + T cell disease (Kaskow and Baecher-Allan 2018), CD8 + T cells have been shown to dominate the T cell infiltrates in active MS lesions (Attfield et al. 2022). Here, CD8A is linked to myeloid sarcoma.