Moreover, increased calpain activity is associated with increased levels of pro-inflammatory Th1 cells in patients with multiple sclerosis (MS) (Figure 4C), and calpain inhibitor treatment of PBMCs isolated from patients with MS decreases T cell proliferation, elevates their indoleamine 2,3-dioxygenase (IDO) levels, and downregulates Th1/Th17 inflammatory cytokines [299,300]. This evidence concerns the gene IDO1 and myeloid sarcoma.