Clinical effect and some pathogenic mechanisms of high dose monomeric IgG therapy in childhood chronic idiopathic thrombocytopenic purpura.

8 children with chronic idiopathic thrombocytopenic purpura received a high dose therapy with monomeric IgG. Before and after the treatment immunological investigations were carried out. All the children showed a positive clinical response, in 5 children there was an increase of thrombocytes to 111-340 X 10(9)/l. A clinico-haematological effect could be shown in those children with an increased percentage of marrow megakaryocytes with IgG fixed on the membrane before treatment. There was no haematological effect neither in cases with fixed IgG and IgA nor IgM and IgA combined, as well as in the case when there was no fixed IgG on the membrane. A steady clinical effect was provided if the number of bone marrow megakaryocytes with fixed IgG reached the norm. The suppression of the synthesis of antithrombocytic antibodies of the same immunoglobulin class can be regarded as a specific mechanism of high IgG doses.