In contrast, activation processes were increased in both compartments for CD4+ (PB +34.8%, CSF +82.6%) as well as CD8+ (PB +90.2%, CSF +17.3%) T cells, indicating distinct and independent T-cell activation processes in PB and CNS, rather than migration of activated peripheral T cells, as the reason for increased intrathecal T-cell proportions in ALS (Fig. 1C). Here, CD4 is linked to amyotrophic lateral sclerosis.