The debate about the relative importance of T cells and B cells in the pathogenesis of MS will be refueled with the long-awaited publication of the results of the failed ATAMS study of atacicept (Kappos et al. Lancet Neurol 2014;13:353-363). Preliminary results from the two atacicept studies, ATAMS in relapsing MS and ATON in optic neuritis, were presented at ECTRIMS 2011 (Kappos et al. Abstract 107; Sergott et al. Abstract P436) and signalled the death knell for the drug in MS.