Monocytes containing at least one GFP+T

Monocytes containing at least one GFP+T. to static conditions (to 45.2% from 10.3%). Infection led to a modest increase in expression of the high affinity conformation of the monocyte integrin Mac-1, and Mac-1 accumulated near endothelial junctions during TEM. Blocking Mac-1 inhibited the crawling and TEM of infected monocytes to a greater degree than uninfected monocytes, and blocking the Mac-1 ligand, ICAM-1, dramatically reduced crawling and TEM for both populations. These findings contribute to a greater understanding of parasite dissemination from the vasculature into tissues. == Introduction == Toxoplasma gondiiis an intracellular apicomplexan parasite that infects virtually all warm-blooded animals. Transmission to Gastrodin (Gastrodine) humans typically occurs by ingestion of parasite tissue cysts or oocysts in contaminated food or water. During acute infection, the bradyzoites or sporozoites within these cysts differentiate into the rapidly dividing tachyzoite form that spreads throughout the body (Montoya and Liesenfeld, 2004). Successful dissemination from the intestine to distal organs occurs due to the parasites ability to cross a wide range of cellular barriers (Barragan and Sibley, 2003), including intestinal epithelium (Dubey, 1997,Dubeyet al., 1997,Barragan and Sibley, 2002), vascular endothelium (Lambertet al., 2006,Furtadoet al., 2012), the blood-brain barrier (Courretet al., 2006,Lachenmaieret al., 2011), the retina (Furtadoet al., 2013), and the maternal-fetal interface (Robbinset al., 2012). Research has demonstrated roles for different types of motile immune cells, including monocytes and dendritic cells (DCs), as Trojan horses forT. gondiidissemination in the host (Tardieux and Menard, 2008). Given the distinct functions and distribution of these immune cell populations, it is likely that they facilitate parasite dissemination in different locations in the body. DCs are predominantly found in tissues and upon activation traffic to lymph nodes, where they serve as antigen-presenting cells to T cells.T. gondiiinfection of DCs induces a hypermigratory phenotype and enhances parasite spread (Lambertet al., 2006). This phenotype is associated with rapid cytoskeletal rearrangement and DC migration (Weidneret al., 2013) and indicates that parasites may disseminate through tissues or to lymph nodes inside DCs (Bierlyet al., 2008). In contrast, monocytes are the major immune cell infected byT. gondiiin Gastrodin (Gastrodine) peripheral blood (Channonet al., 2000), where DCs are present in very low numbers. Since the primary function of monocytes is to migrate from the bloodstream into tissues (Serbinaet al., 2008), they may serve as an ideal vessel for parasite spread from the vasculature into organs. Indeed, infected CD11b+/CD11c-monocytes in the blood have been shown to shuttle parasites to the brain (Courretet al., 2006), and infected CD11b+/CD11c-primary human monocytes migrate more frequently through a blood-brain barrier model than infected CD11c+DC Gastrodin (Gastrodine) (Lachenmaieret al., 2011). Blood vessels in the body are lined with endothelial cells that form an effective biological barrier. The translocation ofT. gondiiacross endothelium in infected human leukocytes has been clearly demonstrated using transwell assays in static conditions (Lambertet al., 2006,Lachenmaieret al., 2011,Furtadoet al., 2012). These assays have contributed important insight into mechanisms ofT. gondiidissemination; however, static transwell assays are not optimal for visualizing and analyzing early, dynamic events in transmigration (i.e., within minutes of contact with the endothelial barrier), and they do not incorporate the conditions of shear stress found in rapidly flowing blood. In Rabbit Polyclonal to OR12D3 the blood, monocytes tether, roll, and firmly adhere to vascular endothelium using a multi-step cascade that involves well described receptor-ligand interactions, many of which are enhanced due to shear force (Leyet al., 2007). Integrins, heterodimeric adhesion molecules on the monocyte surface, play a central role in extravasation by facilitating firm adhesion to endothelium and subsequent searching/crawling to sites of transendothelial migration (TEM) (Herter and Zarbock, 2013). Disrupting the ability of integrins to interact with ligands on endothelium significantly inhibits TEM (Schenkelet al., 2004). However, the dynamics of infected.