Cytotoxic activities of CD8+ T cells collaborate with macrophages to protect against blood-stage murine malaria

Abstract

The protective immunity afforded by CD8+ T cells against blood-stage malaria remains controversial because no MHC class I molecules are displayed on parasite-infected human erythrocytes. We recently reported that rodent malaria parasites infect erythroblasts that express MHC class I antigens, which are recognized by CD8+ T cells. In this study, we demonstrate that the cytotoxic activity of CD8+ T cells contributes to the protection of mice against blood-stage malaria in a FasL-dependent manner. Malaria parasites infected erythroblasts express death receptor Fas. CD8+ T cells induce the extemalization of phosphatidylserine (PS) on the infected erythroblasts in a cell-to-cell contact-dependent manner. PS enhances the engulfment of the infected erythroid cells by phagocytes. T-cell immunoglobulin- and mucin-domain-containing molecule (Tim-4) contributes to the phagocytosis of malaria parasites infected cells as phosphatidylserine receptor. Our findings provide insight into the molecular mechanisms underlying the protective immunity exerted by CD8+ T cells in collaboration with phagocytes.