English: Rickettsiae replicate in ECs and induce local inflammatory reactions. Rickettsiae enter ECs by endocytosis and rapidly escape from the endosome. The bacteria replicate free in the cytosol and are released by different mechanisms. SFG rickettsiae are capable to induce focal lysis while TG rickettsiae replicate in the cell until burst. O. tsutsugamushi induces a kind of budding (a). Rickettsiae infect adjacent ECs, further spread via the blood stream and enter the tissue via local lesions. Infected ECs release a series of chemokines, cytokines, prostaglandins and other factors. Chemokines attract neutrophils, monocytes/MΦ, NK cells and T cells from the periphery into the affected tissue. MΦ and neutrophils both of which also get infected with rickettsiae release NO and ROS which is important for killing of ingested bacteria. The production of NO is supported by IFNγ which is provided by infiltrating NK cells and T cells. MΦ and infiltrating NK and T cells further produce inflammatory cytokines such as TNFα that contribute to local inflammation (b)