a1 Laboratoire de Parasitologie (CNRS URA 1344), Faculté de Méedecine de Grenoble, 38700 La Tranche, France
a2 Laboratoire d'Hématologie, Centre Hospitaller Universitaire de Grenoble, BP 217X, 38043 Grenoble CEDEX, France
Platelets take an active part in immunological processes as well as in haemostasis, especially in the host-parasite relationship. Our aim is to assess the growth of Plasmodium falciparum, cultured in human erythrocytes in the presence of fresh washed human platelets, since thrombocytopaenia is frequently observed during malarial infections. Our results show that platelets induce a dose-related growth inhibition of P. falciparum. Both proliferation and maturation of intraerythrocytic stages of the parasite are inhibited. This growth inhibition is triggered by the parasite itself as neither specific antibodies nor any other components are needed to activate platelets. Activated platelets are directly toxic since complement is not involved. Furthermore, inhibition is not mediated by erythrocyte lysis or by toxic oxygen metabolites. Platelets induce an inhibition of P.falciparum growth, at least in vitro, although the importance of their role played in vivo in malarial immunity has yet to be evaluated.
(Accepted June 20 1989)
p1 Reprint requests to: B. Polack, Laboratoire d'Hematologie, Centre Hospitalier Universitaire, BP 217X, 38043 Grenoble CEDEX, France.