Role of complement in patients with autoimmune hemolytic anemia and platelet transfusion refractoriness.

The complement is a key player of the innate immune response. It provides defense mechanisms that are not specific, but very efficient at neutralizing any invader, accounting for 4% of the proteins in the peripheral blood. Nevertheless, there is a dark side to the complement system, as it may activate its machinery against healthy cells such as peripheral blood red blood cells and platelets resulting in undesired hemolysis and thrombocytopenia, respectively. Understanding and identifying the role of complement in these settings allow physicians to adjust their diagnostic and therapeutic modalities accordingly. The role of complement in the pathophysiology and management of autoimmune hemolytic anemia and of alloimmune-mediated thrombocytopenia is under investigation and discussed.