CD8 T cell clones that can lyse myelin-specific CD4 T cells have been detected in MS patients (Chou et al., 1992; Zhang et al., 1993; Correale et al., 2000), and longitudinal magnetic resonance imaging (MRI) analysis has shown a negative correlation between the percentage of Tc2 cytokine-producing CD8 T cells in the periphery of MS patients and the development of lesions (Killestein et al., 2003). Here, CD8A is linked to myeloid sarcoma.