MPL and autoimmune thrombocytopenic purpura: Additionally the discover of an autoantibody-antigen target, the Mpl TPO receptor (the cellular homolog of the myeloproliferative leukemia virus oncogene), allowed to demonstrate, by using plasma derived from thrombocytopenic ITP patients in MK colony-forming assays, the suppression of MK proliferation by anti-Mpl autoantibodies (50).