FAS and amyotrophic lateral sclerosis: CD8+ lymphocytes infiltrating the spinal cord of a SOD1G93A mouse model of ALS have been shown to interact with MNs through the major histocompatibility complex class I (MHC-I), and they induce killing by involving Fas and granzyme mechanisms [33]; however, the role of CD8+ lymphocytes in ALS, mediated by their interaction with MHC-I, has proven to be rather complex and still unclear.