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Figure 2. Immune checkpoints inhibitor treatment induces reactivation of multiple Sclerosis. PD-1 has been described on autoreactive T cells and TFH cells in multiple sclerosis. The link of PD-1 with the ligand PDL-1 controls T cell activation mantaining tollerance (Healthy). The blocking of PD-1 breaks the tollerance by reactivation of antigen-specific cells and causing damage of the target-cells with persistent inflammation in the CNS (Multiple Sclerosis). Contrary, depletion of PD-1⁺ T cells eliminates activated antigen-specific cells reducing the T cell infiltrates and inflammation in the target-organ (PD-1 blocking). TFH: T Follicular helper cells