Immune reconstitution therapies: concepts for durable remission in multiple sclerosis.

New so-called immune reconstitution therapies (IRTs) have the potential to induce long-term or even permanent drug-free remission in people with multiple sclerosis (MS). These therapies deplete components of the immune system with the aim of allowing the immune system to renew itself. Haematopoietic stem cell transplantation, the oral formulation cladribine and the monoclonal antibodies alemtuzumab, rituximab and ocrelizumab are frequently categorized as IRTs. However, the evidence that IRTs indeed renew adaptive immune cell repertoires and rebuild a healthy immune system in people with MS is variable. Instead, IRTs might foster the expansion of those cells that survive immunosuppression, and this expansion could be associated with acquisition of new functional phenotypes. Understanding immunological changes induced by IRTs and how they correlate with clinical outcomes will be instrumental in guiding the optimal use of immune reconstitution as a durable therapeutic strategy. This Perspectives article critically discusses the efficacy and potential mechanisms of IRTs in the context of immune system renewal and durable disease remission in MS.