B2M and myeloid sarcoma: In order to gauge the potential for CD8+ T cell–mediated targeting of MHC class I–positive neurons and axons in human disease, we immunostained MS and control brain tissues to compare levels of β2-microglobulin (β2M) and HLA-A,B,C expression in neurons in cortical gray matter (cingulate gyrus) and deep gray matter (thalamus).