ABSTRACT
This chapter discusses the evidence for this statement, although the reader must be aware of the fact that evidence obtained using different species within the genus Rickettsia will be generalized, and this is without a certain amount of danger. The rickettsiae are defined simply as obligate intracellular bacteria. As obligate intracellular parasites, they present a unique challenge to the immune system. Experiments were designed to test these findings from the murine model in a larger animal model system that more closely approximates scrub typhus in humans. Depending on the strain of mouse and the strain of R. tsutsugamushi, an intraperitoneal infection will produce either a systemic lethal infection or a chronic immunizing infection. Work in other laboratories has shown that several factors can inhibit la antigen expression on macrophages, including corticosteroids and prostaglandins. The failure to reverse this completely with indomethacin would suggest other factors were being produced by the inflammatory cell population.
