B7 family members and their receptors play a central role in the regulation of T-cell responses through T-cell co-stimulation and co-inhibition pathways that constitute attractive targets for the development of immunotherapeutic drugs. In this study, we report that VSIG-3/IGSF11 is a ligand of B7 family member VISTA/PD-1H and inhibits human T-cell functions through a novel VSIG-3/VISTA pathway. An extensive functional ELISA binding screening assay reveals that VSIG-3 binds to the new B7 family member VISTA but does not interact with other known members of the B7 family. Under the same experimental conditions, we did not observe any significant interaction between VSIG-8 and VISTA. In addition, VSIG-3 inhibits human T-cell proliferation in the presence of T-cell receptor signaling. Furthermore, VSIG-3 significantly reduces cytokine and chemokine production by human T cells including IFN-γ, IL-2, IL-17, CCL5/Rantes, CCL3/MIP-1α, and CXCL11/I-TAC. Anti-VISTA neutralization antibodies attenuate the binding of VSIG-3 and VISTA, as well as VSIG-3-induced T-cell inhibition. Hence, we have identified a novel ligand for VISTA that is able to inhibit human T-cell proliferation and cytokine production. This unique VSIG-3/VISTA co-inhibitory pathway may provide new strategies for the treatment of human cancers, autoimmune disorders, infection, and transplant rejection and may aid in the design of better vaccines.

The apparent complexity of biology increases as more biomolecular interactions that mediate function become known. We have used NMR spectroscopy and molecular modeling to provide direct evidence that tetrameric platelet factor-4 (PF4) and dimeric interleukin-8 (IL8), two members of the CXC chemokine family, readily interact by exchanging subunits and forming heterodimers via extension of their antiparallel ␤-sheet domains. We further demonstrate using functional assays that PF4/IL8 heterodimerization has a direct and significant consequence on the biological activity of both chemokines. Formation of heterodimers enhances the anti-proliferative effect of PF4 on endothelial cells in culture, as well as the IL8-induced migration of CXCR2 vector-transfected Baf3 cells. These results suggest that CXC chemokine biology, and perhaps cytokine biology in general, may be functionally modulated at the molecular level by formation of heterodimers. This concept, in turn, has implications for designing chemokine/cytokine variants with modified biological properties.Platelet factor-4 (PF4) 1 and interleukin-8 (IL8) are members of the CXC chemokine family of small (8 -10 kDa) proteins, a subfamily of chemokines within the cytokine superfamily (1). CXC chemokines are generally chemotactic for migratory immune cells, and thus are involved in the regulation of inflammatory processes and wound healing (1-4). In addition, they demonstrate biological activities in hematopoiesis, cell proliferation, angiogenesis, and glycosaminoglycan binding (1-4).CXC chemokines, which are known to self-associate as dimers and tetramers, exhibit high sequence and three-dimensional structural homology at both the tertiary (monomer) and quaternary (dimer and tetramer) levels. Each folded CXC chemokine monomer has an aperiodic, two-disulfide bond-stabilized N-terminal segment, followed by a three-stranded antiparallel ␤-sheet domain, and a C-terminal ␣-helix that is folded onto the generally amphipathic ␤-sheet (5). Dimers are formed by intermolecularly extending the monomer ␤-sheet into a sixstranded antiparallel ␤-sheet (originally termed AB-type dimer (6)). Tetramers are formed by ␤-sheet sandwiching of two ABtype dimers (6). Native PF4 dimers associate asymmetrically into tetramers (6), whereas in an N-terminal PF4 chimera (PF4M2), dimers associate symmetrically into tetramers with little change in biological activity (7). IL8 forms AB-type dimers and is not known to tetramerize (8 -10).Despite sequence and structure similarities, PF4 and IL8 mediate different biological activities. Although first recognized to bind heparin and act as an anticoagulant, PF4 is also known as an anti-angiogenic agent (11). On the other hand, IL8 binds heparin more weakly and can promote angiogenesis (11,12). The angiogenic functional difference may be due, at least in part, to N-terminal sequence differences. PF4 lacks the IL8 N-terminal tripeptide Glu-Leu-Arg (ELR) motif, which is known to mediate IL8 receptor binding and subsequent signal transduction (13). In additi...

No abstract

1,8-Cineole (eucalyptol), a monoterpene, has been widely reported for the anti-inflammatory effects. Our previous data confirmed that 1,8-cineole ameliorated the inflammatory phenotype of human umbilical vein endothelial cells (HUVECs) by mediating NF-κB expression in vitro. At present, we investigated the protection effects of 1,8-cineole on vascular endothelium in lipopolysaccharide (LPS)-induced acute inflammatory injury mice and the potential mechanisms involved in the protection in HUVECs. Results from enzyme linked immunosorbent assays revealed that 1,8-cineole suppressed the secretion of interleukin (IL)-6 and IL-8 and increased the expression of IL-10 in the serum of LPS-induced mice. 1,8-Cineole reduced the inflammatory infiltration and the expression of vascular cell adhesion molecular 1 (VCAM-1) in the sections of thoracic aorta in LPS-induced acute inflammatory mice. Western blotting indicated that 1,8-cineole significantly decreased the phosphorylation of NF-κB p65 and increased the expression of PPAR-γ in the thoracic aorta tissue. 1,8-Cineole increased the expression of PPAR-γ in LPS-induced HUVECs. 1,8-Cineole and rosiglitazone reduced the protein and mRNA levels of VCAM-1, E-selectin, IL-6, and IL-8 in LPS-induced HUVECs, which could be reversed by the action of GW9662 (inhibitor of PPAR-γ). 1,8-Cineole and rosiglitazone blocked the LPS-induced IκBα degradation and NF-κB p65 nucleus translocation, which could be reversed by the pretreatment of GW9662 or silence of PPAR-γ gene. In conclusion, 1,8-cineole attenuated LPS-induced vascular endothelial cells injury via PPAR-γ dependent modulation of NF-κB.

No abstract