The CD6–CD166/ALCAM interaction has recently been structurally solved (13), and it is long known to be critical for the stabilization and maturation of the immunological synapse (IS) (14–16), as well as for transmigration of T cells to the central nervous system in autoimmune encephalomyelitis (17) and arthritis (18) lesions. This evidence concerns the gene ALCAM and Arthritis.