Reciprocal Th1 and Th17 regulation by mesenchymal stem cells: Implication for multiple sclerosis.

Human mesenchymal stem cells (hMSCs) are being considered for clinical trials of multiple sclerosis (MS). We examined the effects of adult bone marrow-derived hMSCs on responses of primary human Th1, Th17, and Th1/17 double-expressing T-cell subsets, all implicated in MS. As expected, soluble products from hMSCs inhibited Th1 responses; however, Th17 responses were increased. Secretion of interleukin (IL)-10, considered anti-inflammatory, was decreased. Pretreating hMSCs with the proinflammatory cytokine IL-1β accentuated these effects, and caused decreases in the Th1/17 subset. These findings underscore the importance of further preclinical work and immune-monitoring to define hMSC effects on disease-relevant immune responses under variable conditions.