The Vertebrate Host's Immune Response to Plasmodia

Publisher Summary This chapter discusses the vertebrate host's immune response to plasmodia. The vertebrate immune response may be considered to be a triggered cellular cascade, analogous to the molecular cascades that result in blood clotting and complement activation. The function of such cascades in multicellular animals is usually the amplification, direction, and modulation of some primitive function of the organism. The immune response to the asexual blood stages of plasmodia is almost certainly initiated by macrophages oriented toward the blood—such as those of the spleen and bone marrow. The antigen that initiates this response is probably scavenged material released at the time of schizont rupture, and it probably consists of parasite materials not incorporated in the developed merozoites and may include imperfect and damaged merozoites. In addition to the antibody phagocyte-mediated immunity that occurs in the immune or pre-immune animal, there appear to be other mechanisms of host defense against plasmodia that occur during the crisis stage of infection. These mechanisms are immunological, in that they are induced by antigenic materials, but they do not have immunological specificity in the sense of an antigen–antibody reaction. These mechanisms include reticuloendothelial, particularly macrophage, activation, attendant splenic hypertrophy, and the production of increased amounts of autoantibodies to modified or enzymatically exposed host erythrocyte membrane materials.