In Vitro Interactions Between Human Peripheral Macrophages and Rickettsia Mooseri

Abstract

Recovery from typhus infection is usually associated with the development of strong immunity to re-infection. An array of immunoglobulins is produced as well as a state of delayed type hypersensitivity. The contribution of the delayed type hypersensitivity to immunity and pathogenesis of disease, though currently under investigation, is unknown. However, it has long been known that passive transfer of serum from an immune subject will confer protection to a non-immune subject, and, hence, humoral antibodies probably play a significant role in immunity. Although serum antibodies display a wide variety of properties, such as agglutination, fixation of complement, opsonization, neutralization of toxic action, etc., studies in our laboratory have shown that these antibodies do not have a direct rickettsiacidal action even when supplemented with complement, lysozyme, etc. Accordingly, it has been postulated that antibodies must act in conjunction with some other component of the defense mechanism such as phagocytic cells, It has been shown in our laboratories that although typhus rickettsiae are readily taken up by macrophage-like cells derived from human peripheral monocytes in cell culture, these cells alone do not destroy the rickettsiae. Instead, the organisms multiply and eventually destroy the cell. However, if the rickettsiae are first exposed to immune serum and are then ingested by these macrophages, they are readily destroyed within the cells.