[Platelet antibody activity in malaria thrombocytopenia]

To assess immune responses to malaria-induced thrombocytopenia, an haematologic and immunologic study was performed on 25 patients with imported malaria upon admission and 8 days after treatment. Thrombocytopenia (150 x 10(9)/litre) was detected in 19 cases (P. falciparum: 11 cases, P. ovale: 6 cases, P. vivax: 2 cases). No laboratory evidence of disseminated intravascular coagulation impairment was found in any of the patients. Bone marrow examination performed in 9 cases showed no abnormality in the megakaryocyte series. Platelet count was independent of circulating parasite levels (r = 0.27) and inversely related to the number of antibody binding sites (ABS) on platelets (r = -0.6, p. less than 0.01). The indirect Coombs test (r = -0.54; p less than 0.01) and IgG and IgE levels (p less than 0.02) gave similar findings. A statistical correlation was observed between the level of circulating immune complex and the number of ABS (r = 0.525, p less than 0.01). Thus malaria-induced thrombocytopenia seems to mainly involve IgG type antiplatelet antibody activity. Although they may be implicated in the binding of antibodies to platelets, circulating immune complexes do not appear to mediate thrombocytopenia.