Acanthamoeba Activates Macrophages Predominantly through Toll-Like Receptor 4- and MyD88-Dependent Mechanisms To Induce Interleukin-12 (IL-12) and IL-6.

is a ubiquitous free-living amoeba with a worldwide distribution that can occasionally infect humans, causing particularly severe infections in immunocompromised individuals. Dissecting the immunology of infections has been considered problematic due to the very low incidence of disease, despite the high exposure rates. While macrophages are acknowledged as playing a significant role in infections, little is known about how this facultative parasite influences macrophage activity. Therefore, in this study we investigated the effects of on the activation of resting macrophages. Consequently, murine bone marrow-derived macrophages were cocultured with trophozoites of either the laboratory Neff strain or a clinical isolate of real-time imaging demonstrated that trophozoites of both strains often established evanescent contact with macrophages. Both strains induced a proinflammatory macrophage phenotype characterized by the significant production of interleukin-12 (IL-12) and IL-6. However, macrophages cocultured with the clinical isolate of produced significantly less IL-12 and IL-6 than the Neff strain. The utilization of macrophages derived from MyD88-, TRIF-, Toll-like receptor 2 (TLR2)-, TLR4-, and TLR2/4-deficient mice indicated that -induced proinflammatory cytokine production was through MyD88-dependent, TRIF-independent, TLR4-induced events. This study shows for the first time the involvement of TLRs expressed on macrophages in the recognition of and response to trophozoites.