1,523 publications from this institution
Malaria is still a life-threatening infectious disease that continues to produce 2 million deaths annually. Malaria parasites have acquired immune escape mechanisms and prevent the development of sterile immunity. Regulatory T cells (Tregs) have been reported to contribute to immune evasion during malaria in mice and humans, suggesting that activating Tregs is one of the mechanisms by which malaria parasites subvert host immune systems. However, little is known about how these parasites activate Tregs. We herein show that TLR9 signaling to dendritic cells (DCs) is crucial for activation of Tregs. Infection of mice with the rodent malaria parasite Plasmodium yoelii activates Tregs, leading to enhancement of their suppressive function. In vitro activation of Tregs requires the interaction of DCs with parasites in a TLR9-dependent manner. Furthermore, TLR9−/− mice are partially resistant to lethal infection, and this is associated with impaired activation of Tregs and subsequent development of effector T cells. Thus, malaria parasites require TLR9 to activate Tregs for immune escape.
Aims Lymphangiogenesis is frequently observed during inflammation, and this inflammation-induced lymphangiogenesis (IL) is a phenomenon actively involved in the pathophysiology of inflammation. We explored the roles of an inducible prostaglandin E synthase, mPGES-1, in IL elicited by lipopolysaccharide (LPS). Main methods Peritonitis was induced in mice by intraperitoneal injection of LPS (E. coli 0111-B4; 25μg/mouse every 2days), and IL was evaluated by LYVE-1 immunostaining of whole-mount diaphragm tissues. Key findings Compared to vehicle-treated wild-type (WT) mice, lymphatics in the diaphragms of mice injected with LPS were widened and the number of LYVE-1-positive ladder-structured lymphatics increased temporally. This increase in lymphangiogenesis was accompanied by increased expression of vascular endothelial growth factor (VEGF)-C/D in the diaphragms. In mice treated with celecoxib, a cyclooxygenase-2 inhibitor, IL was suppressed with reduced expression of VEGF-C/D. This was also observed in mPGES-1 knockout mice (KO). Immunoreactive COX-2 and mPGES-1 were detected in both CD11b-positive and CD3ε-positivecells in the diaphragm. When FITC–dextran was injected into the peritoneal cavities, the amount of residual FITC–dextran was reduced significantly in WT mice injected with LPS, and this reduction was significantly decreased in mPGES-1 KO mice. Significance The present results suggest that mPGES-1 plays a significant role in lymphangiogenesis during inflammation, and represents a novel target for controlling IL.
