The anti-malaria role of the spleen

Immunity: The anti-infectious effect of the spleen in general and its anti- malarial effect has been known for a long time. This effect is associated, among other functions, with the spleen's capacity to filter and destroy ery throcytes parasitized by plasmodies or altered by various physical (heat... ) or chemical factors. In addition, splenic immunity, which associates spec ific and nonspecific humoral and cellular effector mechanisms is no longer a question of debate. Open questions: There remains nevertheless one aspect of the question to be elucidated: the probable interaction between this immunity and other (gene tic...) factors of the malarious host. Cell functions: This article summarizes current knowledge in connection wit h: a) participation of various cell populations in the mechanisms of spleni c filtration and phagocytosis and b) genesis of a repertory of B and T lymp hocytes, plasmodio-specific memory cells. During an infection, lymphocytes, monocytes and macrophages are recruited from peripheral blood and, in coop eration with cells known as "barrier" cells, increase the capacity of splen ic filtration/purge and phagocytosis. In addition, the appearance of B and T lymphocytes with specific memory of P. falciporum result from hypermutati on in VH genes (for B lymphocytes) or from clonal selection (for T lymphocy tes). The folicular dendritic cells accomplish a reserve function. By const antly releasing the antigen, these cells would contribute to maintaining im mune memory or to stimulating naive cells. Further studies are necessary to better understand the role of the splenic microcirculation and to identify parasite components which stimulate the protective response of the spleen against plasmodies. (C) 2000, Masson. Paris.