ADAMTS13 and thrombotic thrombocytopenic purpura: (55), it was found that switching anti – ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) to the IgG4 subclass had a protective effect in a IgG4-mediated disease, thrombotic thrombocytopenic purpura (TTP), in contrast to IgG3 anti-ADAMTS13 antibodies.