C-type lectin receptor SIGNR1 expressed on peritoneal phagocytic cells with an immature dendritic cell-like phenotype is involved in uptake of oligomannose-coated liposomes and subsequent cell maturation

C-Type Lectin Receptors in Antiviral Immunity and Viral Escape

C-type lectin receptors (CLRs) are important pattern recognition receptors involved in recognition and induction of adaptive immunity to pathogens. Certain CLRs play an important role in viral infections as they efficiently interact with viruses. However, it has become clear that deadly viruses subvert the function of CLRs to escape antiviral immunity and promote infection. In particular, viruses target CLRs to suppress or modulate type I interferons that play a central role in the innate and adaptive defense against viruses. In this review, we discuss the function of CLRs in binding to enveloped viruses like HIV-1 and Dengue virus, and how uptake and signaling cascades have decisive effects on the outcome of infection.

The Peritoneal Macrophages in Inflammatory Diseases and Abdominal Cancers

Peritoneal macrophages (PMs) are the major cell type of peritoneal cells that participate in multiple aspects of innate and acquired immunity in the peritoneal cavity. PMs have an ability to release a large amount of proinflammatory and anti-inflammatory cytokines and therefore play a critical role in regulating the differentiation of innate immune cells and inflammatory T cells. Accumulating studies demonstrate that the immunological reactions and inflammatory responses of PMs are strongly related to the pathogenic processes of various inflammatory diseases and abdominal cancers. Consequently, the regulation of PM activation has gradually emerged as a promising target for immunotherapy, and better understanding of the distinctly biological function of PMs in individual diseases is crucial for designing specific and effective therapeutic agents. This review covers the characterization and immunological function of PMs in hosts with inflammatory diseases and abdominal cancers.

Requirement of TLR4 signaling for the induction of a Th1 immune response elicited by oligomannose-coated liposomes

We have previously demonstrated that administration of oligomannose-coated liposomes (OMLs), in which an antigen is encased, induce antigen-specific Th1 immune responses and CTLs. In the present study, we showed that TLR4 signaling is required for the induction of specific immune responses following OML administration. In C3H/HeJ mice, which express a dysfunctional TLR4, the antigen-specific Th1 immune response could not be elicited following intraperitoneal administration of OVA-encased OMLs (OML/OVA). However, OML uptake by peritoneal cells, the subsequent production of IL-12 and the upregulation of co-stimulatory molecules and MHC class II on the cells in response to OML uptake occurred in C3H/HeJ mice to the same extent as in wild type C3H/HeN mice. In addition, peritoneal phagocytic cells from TLR4(-/-) mice that ingest OML/OVA can activate CD4(+) T cells from OT-II mice. On the other hand, the number of OML-ingesting peritoneal cells that migrated into mesenteric lymph nodes in C3H/HeJ mice was significantly less than that in C3H/HeN mice. Therefore, the chemotactic capability of OML-ingesting peritoneal phagocytes to the draining lymph nodes rather than the activation and maturation of the cells in response to OML uptake is impaired by lack of TLR4 signaling, and disorder of the Th1 immune response elicited by OMLs in mice, which lack TLR4 signaling, is due to the impairment of cell migration following OML uptake.