Effects of lethal and non-lethal malaria on the mononuclear phagocyte system

Abstract

The effects ofone non-lethal species ofmalarialparasite, Plasmodium yoelii, and one lethal species, P. berghei, on the mononuclear phagocyte system (MPS) BA LB /c mice).The mononuclear phagocyte system (MPS) represents a major site of interactions between malarial parasite and the host. During infection, macrophages perform a crucial role in the clearance of parasites 2, and also appear to play a part in the modulation of the immune response 21. It is therefore conceivable that the particular way in which this interaction occurs may influence the outcome of the infec tion. This possibility was investigated in two murine malarias, one lethal caused by Plasmo dium berghei, and one self-limiting caused by P. yoelii. M A T E R IA LS AN D M ETHODS Host-parasite systemsTwo to four month old female BALB/c mice bred in our Animal Unit were used throughout Recebido para publicação em 0 3 /0 1 /8 3 this study. They were infected with 105 parasitized erythrocytes i.v. of either P. yoelii strain 17X or P. berghei A N K A strain, which were maintained as frozen stabilates and passed once in isogenic mice before use. P yoelii 17X causes a self-curing infection after an acute attack lasting 2-3 weeks, while P. berghei gives rise to a lethal infection with two peaks of mortality, on days 6-8 and 21-23. Histological techniquesLivers and spleens were fixed in Carno/s solution and stained either with haematoxylineosin, Giemsa solution, pyronin-methyl green, <md silver impregnation for reticulin s . The first two methods were also used for staining the bone marrow.58

Stages of in vitro phagocytosis of Plasmodium falciparum-infected erythrocytes by human monocytes

“…Peripheral blood monocytes 13 and spleen and liver macrophages 11 show considerable phagocytic activity towards parasitized erythrocytes, particularly when anti-parasite antibodies are present 4 10 . It has been shown that monocytes plus anti-plasmodial antibodies are able to decrease the in vitro growth of Plasmodium falciparum by nearly 80% 7 .…”