ECs, that are besides macrophages the major target cells for rickettsial infections [8–12], react to infection with TG and SFG rickettsia with the production of proinflammatory cytokines like IL-1 (interleukin-1), IL-6 and TNFα (tumor necrosis factor-α), chemokines like IL-8, IP-10 (interferon-γ induced protein-10) and MCP-1 (monocyte chemotactic protein-1) and other mediators in vitro that lead to activation and recruitment of immune cells to the site of infection [8, 13–17]. Here, IL6 is linked to infection.