Role of Bone Marrow-derived Mesenchymal Stem Cell Defects in CD8 CD28 Suppressor T-lymphocyte Induction in Patients with Immune Thrombocytopenia and Associated Mechanisms

Many immune dysfunctions participate in immune thrombocytopenia (ITP) pathogenesis, including numeric and functional defects in suppressor T (Ts) cells and immune-regulation abnormalities in mesenchymal stem cells (MSCs). Recent studies showed that MSCs can promote Ts cell differentiation. Thus, we compared the Ts cell induction ability of bone marrow-derived MSCs (BM-MSCs) between patients with ITP and normal controls (NCs), and examined the mechanism of this difference. Co-culture of CD8 T cells with BM-MSCs revealed that BM-MSCs elevated Ts cell percentage and function, but the efficiency was lower in patients with ITP than in NCs. Blockade experiments showed that blockade of interleukin 6 (IL-6) partially reversed Ts cell induction by BM-MSCs. Addition of exogenous IL-6 down-regulated Ts cell apoptosis. Moreover, BM-MSCs enhanced IL-10 secretion and inhibition ability of Ts cells. IL-6 secretion, regulatory abilities of IL-10 expression in Ts cells, and the enhanced efficiency of Ts cells inhibition function by BM-MSCs were all decreased in patients with ITP. All-trans retinoic acid preconditioning promoted BM-MSC induction of Ts cell percentages and umbilical cord-derived (UC) MSCs efficiently improved ITP Ts cell numbers and dysfunction. In conclusion, defects of BM-MSCs in Ts cell induction are involved in ITP pathogenesis, and exogenous UC-MSCs may be useful for ITP therapy.