It remains unclear how these changes in the B\cell compartment associate with disease activity in MS and it is also unclear if these effects are sustained over time. sclerosis Multiple sclerosis (MS) can be broadly divided into two, often overlapping clinical courses: that of relapsing MS, characterized by clearly defined attacks of new or worsening neurological symptoms, or progressive MS where there is worsening neurological function independent of relapses. Clinical trials over the last 25?years have been productive in discovering an ever increasing list of medications effective in preventing relapses. However, the search for therapies to reduce or halt progression in progressive MS has remained elusive until recently, when a new anti\CD20 monoclonal antibody (mAb), ocrelizumab, was found to significantly reduce progression in a phase III trial for primary progressive MS (Montalban (2015) up\regulates CD80 and CD86 when activated. Additionally, CD80 and CD86 expression is higher in MS patients than in healthy controls, and CD80+ lymphocyte levels increase in MS patients during exacerbations (Aung and Balashov, 2015). Therefore, B\cells may be involved in MS not just as sources of GSN cytokines and autoantibodies, but also as APCs that stimulate T\cells. Although the adaptive immune system has not been traditionally viewed as playing a role in progressive MS, descriptions of lymphoid follicle\like structures in the meninges surrounding CNS tissue of secondary progressive MS cases suggest that B\cells could also play a role in progressive disease (Serafini (II)38 Ofatumumab i.v. 100, 300 and 700?mgdemonstrated superiority of natalizumab over platform therapies when used Darapladib first\line in treatment\na?ve RRMS patients, with a 68% relative reduction in ARR (Spelman (Kircher (Bielekova demonstrated safety and efficacy of rituximab, comparable to that reported in earlier trials (Salzer found superior efficacy and tolerability of rituximab, compared with Darapladib fingolimod, in 256 stable RRMS patients who had switched from natalizumab due to JCV antibody positivity (Alping studies have shown that ofatumumab depletes B\cell lines resistant to rituximab (Wierda (2014) demonstrated that replenishing B\cells largely comprise the na?ve (IgD+/CD27?) and Darapladib transitional B\cell subsets, possibly derived from pro\ B\cells that do not express CD20. The repletion of memory B\cell subsets was more delayed, occurring from Darapladib around 37C52?weeks. It remains unclear how these changes in the B\cell compartment associate with disease activity in MS and it is also unclear if these effects are sustained over time. Nonetheless, the capacity for memory B\cell numbers to recover over time suggests that some maintenance therapy may be required to achieve sustained therapeutic benefit with CD20 mAb therapies. Although no significant effects on CD3+ T\lymphocyte cells were reported in the HERMES and OLYMPUS trials for rituximab in MS, there is some evidence to suggest that rituximab therapy could deplete a small subset of CD3+ CD20dim T\cells (<10% of total CD3+ cells) as part of its actions in MS (Palanichamy (Schuh et al., 2016), it is not known if these cells contribute to MS pathogenesis or if their depletion is part of the mechanisms of rituximab therapy in MS. It is possible therefore that CD20 mAb therapies may directly target both the B\cell and T\cell functions as part of their mechanisms in MS. Other B\cell therapies in development for MS In addition to the CD20 mAb therapies, several other biologicals targeting B\cell surface antigens or B\cell cytokine Darapladib signalling molecules have also been trialled for MS. Importantly, the use of targeted therapeutics to modify B\cell functions has already begun to provide novel and often unexpected insights into the functions of B\cells in MS pathogenesis, suggesting that they are important contributors to immune regulation in MS. CD19 mAb therapies The CD19 antigen is expressed throughout B\cell development and, in contrast to the CD20 antigen, is also present on plasma.