Efficacy of rhesus antibodies (Anti-Rh0 (D)) in autoimmune thrombocytopenia: correlation with response to high dose IgG and the degree of haemolysis.

We have compared the efficacy of high-dose IgG with that of Rhesus antibodies (anti-Rh0 (D)) in 5 patients with autoimmune thrombocytopenic purpura (3 adults and 2 children). Although only transient, high-dose IgG (0.4 g/kg X 5 days) was effective in all patients (peak values 50-200 X 10(9)/1), whereas anti-Rh0 (D) (11-20 micrograms/kg X 5 days) led to comparable results in only 3 patients (165 X 10(9)/1, 72 X 10(9)/1, 33 X 10(9)/1). This response to anti-Rh0 (D) was neither related to the degree of induced haemolysis (increase of LDH and decrease of haptoglobin) nor to the amount of IgG antibodies bound to red blood cells, as quantified by the 125-I-antiglobulin test. A decrease of platelet-associated IgG was recorded in 3 patients: 2 of them showed an improvement of platelet counts and in one of them there was no response. We conclude that the therapeutic response of high-dose IgG and anti-Rh0 (D) is independent of the degree of induced haemolysis and may not be predicted from the effectiveness of either therapy alone.