ABSTRACT
Triggering receptor expressed on myeloid cells (TREM)-1 is an orphan receptor implicated in innate immune activation. Inhibition of TREM-1 reduces sepsis in mouse models, suggesting a role for it in immune responses triggered by bacteria. However, the absence of an identified ligand has hampered a full understanding of TREM-1 function. We identified complexes between peptidoglycan recognition protein 1 (PGLYRP1) and bacterially derived peptidoglycan that constitute a potent ligand capable of binding TREM-1 and inducing known TREM-1 functions. Interestingly, multimerization of PGLYRP1 bypassed the need for peptidoglycan in TREM-1 activation, demonstrating that the PGLYRP1/TREM-1 axis can be activated in the absence of bacterial products. The role for PGLYRP1 as a TREM-1 activator provides a new mechanism by which bacteria can trigger myeloid cells, linking two known, but previously unrelated, pathways in innate immunity.
Subject(s)
Cytokines/immunology , Immunity, Innate/immunology , Membrane Glycoproteins/immunology , Neutrophils/immunology , Receptors, Immunologic/immunology , Humans , Immunoprecipitation , Ligands , Surface Plasmon Resonance , Triggering Receptor Expressed on Myeloid Cells-1ABSTRACT
Members of the CD28 family play important roles in regulating T-cell functions and share a common gene structure profile. We have identified VSTM3 as a protein whose gene structure matches that of the other CD28 family members. This protein (also known as TIGIT and WUCAM) has been previously shown to affect immune responses and is expressed on NK cells, activated and memory T cells, and Tregs. The nectin-family proteins CD155 and CD112 serve as counter-structures for VSTM3, and CD155 and CD112 also bind to the activating receptor CD226 on T cells and NK cells. Hence, this group of interacting proteins forms a network of molecules similar to the well-characterized CD28-CTLA-4-CD80-CD86 network. In the same way that soluble CTLA-4 can be used to block T-cell responses, we show that soluble Vstm3 attenuates T-cell responses in vitro and in vivo. Moreover, animals deficient in Vstm3 are more sensitive to autoimmune challenges indicating that this new member of the CD28 family is an important regulator of T-cell responses.
Subject(s)
CD28 Antigens/immunology , Receptors, Immunologic/immunology , T-Lymphocytes/immunology , Animals , Autoimmune Diseases/immunology , Cells, Cultured , Dendritic Cells/immunology , Humans , Mice , Rats , Receptors, Immunologic/deficiency , T-Lymphocytes/chemistryABSTRACT
Cancer development is often associated with the lack of specific and efficient recognition of tumor cells by the immune system. Natural killer (NK) cells are lymphocytes of the innate immune system that participate in the elimination of tumors. We report the identification of a tumor cell surface molecule that binds NKp30, a human receptor which triggers antitumor NK cell cytotoxicity and cytokine secretion. This previously unannotated gene belongs to the B7 family and, hence, was designated B7-H6. B7-H6 triggers NKp30-mediated activation of human NK cells. B7-H6 was not detected in normal human tissues but was expressed on human tumor cells, emphasizing that the expression of stress-induced self-molecules associated with cell transformation serves as a mode of cell recognition in innate immunity.
Subject(s)
Antigens, CD/immunology , B7-1 Antigen/immunology , Killer Cells, Natural/immunology , Ligands , Lymphocyte Activation , Natural Cytotoxicity Triggering Receptor 3/immunology , Amino Acid Sequence , Animals , Antigens, CD/genetics , Antigens, Surface/immunology , B7 Antigens , B7-1 Antigen/genetics , Cell Line, Tumor/immunology , Female , Humans , Immunity, Innate/immunology , Immunoglobulin Fc Fragments/genetics , Immunoglobulin Fc Fragments/immunology , K562 Cells , Killer Cells, Natural/cytology , Mice , Mice, Inbred BALB C , Molecular Sequence Data , Natural Cytotoxicity Triggering Receptor 3/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/immunologyABSTRACT
The proinflammatory cytokines IL-17A and IL-17F have a high degree of sequence similarity and share many biological properties. Both have been implicated as factors contributing to the progression of inflammatory and autoimmune diseases. Moreover, reagents that neutralize IL-17A significantly ameliorate disease severity in several mouse models of human disease. IL-17A mediates its effects through interaction with its cognate receptor, the IL-17 receptor (IL-17RA). We report here that the IL-17RA-related molecule, IL-17RC is the receptor for IL-17F. Notably, both IL-17A and IL-17F bind to IL-17RC with high affinity, leading us to suggest that a soluble form of this molecule may serve as an effective therapeutic antagonist of IL-17A and IL-17F. We generated a soluble form of IL-17RC and demonstrate that it effectively blocks binding of both IL-17A and IL-17F, and that it inhibits signaling in response to these cytokines. Collectively, our work indicates that IL-17RC functions as a receptor for both IL-17A and IL-17F and that a soluble version of this protein should be an effective antagonist of IL-17A and IL-17F mediated inflammatory diseases.
