Mast Cell Costimulation by CD226/CD112 (DNAM-1/Nectin-2)

A novel interface consisting of homologous immunoglobulin superfamily members with multiple functions

Immunoglobulin superfamily (IgSF) members account for a large proportion of cell adhesion molecules that perform important immunological functions, including recognizing a variety of counterpart molecules on the cell surface or extracellular matrix. The findings that CD155/poliovirus receptor (PVR) and CD112/nectin-2 are the ligands for CD226/platelet and T-cell activation antigen 1 (PTA1)/DNAX accessory molecular-1 (DNAM-1), CD96/tactile and Washington University cell adhesion molecule (WUCAM) and that CD226 is physically and functionally associated with lymphocyte function-associated antigen-1 (LFA-1) on natural killer (NK) and activated T cells have largely expanded our knowledge about the functions of CD226, CD96, WUCAM and LFA-1 and their respective ligands, CD155, CD112, intercellular adhesion molecule (ICAM)-1 and junctional adhesion molecule (JAM)-1. The interactions of these receptors and their ligands are involved in many key functions of immune cells including naive T cells, cytotoxic T cells, NK cells, NK T cells, monocytes, dendritic cells, mast cells and platelets/megakaryocytes.

Molecular cloning, characterization and three-dimensional modeling of porcine nectin-2/CD112

Nectin-2, also known as poliovirus receptor-related 2 or CD112, has been identified in many animals and plays a crucial role in cell recognition and adhesion. Here we report the identification of two porcine Nectin-2 (poNectin-2) isoforms. The open reading frame (ORF) of 1440 nucleotides (nt) of poNectin-2alpha encodes 479 amino acids (aa). poNectin-2delta gene consists of 1620nt of ORF with 539aa. The deduced aa sequences of poNectin-2alpha and poNectin-2delta gene exhibit high identity with human (74% and 79%) and mouse (71% and 76%) orthologs, respectively. The ectodomains of deduced poNectin-2 protein share the structural feature of mammalian Nectin-2, including a conserved cysteine skeleton important for the formation of the three-dimensional structure. RT-PCR analysis showed that the mRNA of both poNectin-2 isoforms was broadly expressed in various tissues and cells. poNectin-2 gene was mapped to chromosome 6q21. Information from this study will help to elucidate the Nectin-2 pathway in xenotransplant immunity.

Localization of CD226 in the mouse hippocampus and cerebellum during adulthood and postnatal development

CD226, a member of cell adhesion molecules, has been widely studied in the immune system; however, its expression in the CNS remains unknown. In our present study, we detected CD226 mRNA and protein in the mouse hippocampus and cerebellum by RT-PCR and Western blotting, respectively. Immunohistochemical studies found that CD226 is primarily located in the hilus of the dentate gyrus and stratum lucidum aligned along the pyramidal cells in the hippocampal CA3 area, the interspaces of granular cells and the somata of the Purkinje cells in the cerebellar cortex during adulthood. Double-staining results revealed that CD226 co-localized well with synaptic marker proteins including synaptophysin, syntaxin and PSD-95. During postnatal development, CD226 could not be detected at its adult locations until postnatal day 12; however, it was temporally expressed in the somata of neighboring or distant nuclei associated with its adult location. These results showed the diverse localization of CD226 in the mouse hippocampus and cerebellum for the first time and suggested its potential role in the CNS.

Human mast cell activation by Staphylococcus aureus: interleukin-8 and tumor necrosis factor alpha release and the role of Toll-like receptor 2 and CD48 molecules

The ability of Staphylococcus aureus to invade and survive within host cells is believed to contribute to its propensity to cause persistent and metastatic infections. In addition, S. aureus infections often are associated with atopic diseases such as dermatitis, rhinitis, and asthma. Mast cells, the key cells of allergic diseases, have a pivotal role in innate immunity and have the capacity of phagocytosis, and they can destroy some pathogenic bacteria. However, little is known about the ability of some other bacteria to survive and overcome mast cell phagocytosis. Therefore, we were interested in evaluating the interplay between mast cells and S. aureus. In this study, we show that human cord blood-derived mast cells (CBMC) can be infected by pathogenic S. aureus. S. aureus displayed a high adherence to mast cells as well as invasive and survival abilities within them. However, when infections were performed in the presence of cytochalasin D or when CBMC were preincubated with anti-Toll-like receptor 2 (TLR2) or anti-CD48 antibodies, the invasiveness and the inflammatory response were abrogated, respectively. Furthermore, we observed an increase of TLR2 and CD48 molecules on CBMC after S. aureus infection. The infection of CBMC with S. aureus also caused the release of tumor necrosis factor alpha (TNF-alpha) and interleukin-8 (IL-8). Both live and killed S. aureus organisms were found to trigger TNF-alpha and IL-8 release by CBMC in a time-dependent manner. Cumulatively, these findings suggest that S. aureus internalizes and survives in mast cells. This may play an important role in infections and in atopic diseases associated with S. aureus.

Mast cells as effector cells: a co-stimulating question

Mast cells are currently recognized as effector cells in many settings beyond just allergic reactions, including innate immunity, autoimmunity, chronic inflammatory disorders and atherosclerosis. Signaling pathways of the mast cell response have been widely explored in the past but these are still linked with single axes, such as the high affinity IgE receptor FcepsilonRI, presumably an exclusive determinant of the magnitude of the response to allergen. By contrast, the T cell receptor is viewed as a rich complex of stimulatory and co-stimulatory molecules, setting an array of thresholds to ensure a highly regulated response. Recent observations show that mast cells express various classes of co-stimulatory molecules that modulate their function. These molecules might therefore contribute to the outcome of mast cell-associated pathologies, and constitute new therapeutic targets in such diseases.