Corticosteroid administration depresses circulating dendritic cells in ITP patients

Idiopathic or immune thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by low platelet count resulting from antibody-mediated destruction of platelets. The production of these IgG anti-platelet autoantibodies is critically governed by T-lymphocytes which can be activated by antigen-presenting cells (APC) such as dendritic cells. We hypothesized that one of the mechanisms by which corticosteroid administration can suppress the immune system is to depress the number of circulating dendritic cells production in ITP patients. Dendritic cell population was measured in peripheral blood of three ITP patients before and after the administration of prednisone. Both counts of myeloid and lymphoid dendritic cells in the blood of ITP patients were greatly reduced after the administration of prednisone. The decrease in circulating dendritic cells is associated with the increase of platelets in circulation with the treatment of prednisone. These results suggest that corticosteroid therapy may decrease the effects of the autoantibody on platelets in ITP patients by reduce the number of circulating dendritic cells.