Low molecular weight fragmentation products of the polysaccharide of Hyaluronic acid (sHA) produced during inflammation have been shown to be potent activators of immunocompetent cells such as dendritic cells (DCs) and macrophages. Here we report that sHA induces maturation of DCs via the Toll-like receptor (TLR)-4, a receptor complex associated with innate immunity and host defense against bacterial infection. Bone marrow–derived DCs from C3H/HeJ and C57BL/10ScCr mice carrying mutant TLR-4 alleles were nonresponsive to sHA-induced phenotypic and functional maturation. Conversely, DCs from TLR-2–deficient mice were still susceptible to sHA. In accordance, addition of an anti–TLR-4 mAb to human monocyte–derived DCs blocked sHA-induced tumor necrosis factor α production. Western blot analysis revealed that sHA treatment resulted in distinct phosphorylation of p38/p42/44 MAP-kinases and nuclear translocation of nuclear factor (NF)-κB, all components of the TLR-4 signaling pathway. Blockade of this pathway by specific inhibitors completely abrogated the sHA-induced DC maturation. Finally, intravenous injection of sHA-induced DC emigration from the skin and their phenotypic and functional maturation in the spleen, again depending on the expression of TLR-4. In conclusion, this is the first report that polysaccharide degradation products of the extracellular matrix produced during inflammation might serve as an endogenous ligand for the TLR-4 complex on DCs.

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Protocol-guided weaning of mechanical ventilation, as performed by nurses and respiratory therapists, is safe and led to extubation more rapidly than physician-directed weaning.

An organized approach to the hemodynamic support of sepsis was formulated. The fundamental principle is that clinicians using hemodynamic therapies should define specific goals and end points, titrate therapies to those end points, and evaluate the results of their interventions on an ongoing basis by monitoring a combination of variables of global and regional perfusion. Using this approach, specific recommendations for fluid resuscitation, vasopressor therapy, and inotropic therapy of septic in adult patients were promulgated.

The extracellular matrix component hyaluronan (HA) exists physiologically as a high m.w. polymer but is cleaved at sites of inflammation, where it will be contacted by dendritic cells (DC). To determine the effects of HA on DC, HA fragments of different size were established. Only small HA fragments of tetra- and hexasaccharide size (sHA), but not of intermediate size (m.w. 80,000–200,000) or high m.w. HA (m.w. 1,000,000–600,000) induced immunophenotypic maturation of human monocyte-derived DC (up-regulation of HLA-DR, B7-1/2, CD83, down-regulation of CD115). Likewise, only sHA increased DC production of the cytokines IL-1β, TNF-α, and IL-12 as well as their allostimulatory capacity. These effects were highly specific for sHA, because they were not induced by other glycosaminoglycans such as chondroitin sulfate or heparan sulfate or their fragmentation products. Interestingly, sHA-induced DC maturation does not involve the HA receptors CD44 or the receptor for hyaluronan-mediated motility, because DC from CD44-deficient mice and wild-type mice both responded similarly to sHA stimulation, whereas the receptor for hyaluronan-mediated motility is not detectable in DC. However, TNF-α is an essential mediator of sHA-induced DC maturation as shown by blocking studies with a soluble TNFR1. These findings suggest that during inflammation, interaction of DC with small HA fragments induce DC maturation.

Cellular adhesion by classical cadherins depends critically on the exact proteolytic removal of their N-terminal prosequences. In this combined solution NMR and X-ray crystallographic study, the consequences of propeptide cleavage of an epithelial cadherin construct (domains 1 and 2) were followed at atomic level. At low protein concentration, the N-terminal processing induces docking of the tryptophan-2 side-chain into a binding pocket on the same molecule. At high concentration, cleavage induces dimerization (K D ¼ 0.72 mM, k off ¼ 0.7 s À1 ) and concomitant intermolecular exchange of the bA-strands and the tryptophan-2 side-chains. Thus, the cleavage represents the switch from a nonadhesive to the functional form of cadherin.

IntroductionOsteopontin (OPN) is a secreted phosphoprotein that contains an integrin-binding arginine-glycine-aspartate sequence (RGD) motif. OPN has proinflammatory cytokine and chemokine functions in cell-mediated immunity. [1][2][3][4] A number of studies have demonstrated that OPN critically contributes to the development of T helper 1 (Th1)-mediated immunity and disease. 5,6 Among other reports, OPN-deficient mice develop disseminated infection and have a delayed ability to clear disease when infected with Mycobacterium bovis (BCG). 7 In murine models of autoimmune encephalomyelitis, a model of human multiple sclerosis that critically depends upon the balance of Th-shaping cytokines such as interleukin-10 (IL-10) and IL-12, OPN-deficient mice develop milder disease. 8,9 Corneal infection of OPN-deficient mice with herpes simplex virus 1 (HSV-1) is followed by a reduced delayedtype hypersensitivity to HSV. 6 We have shown that OPN-deficient mice have an impaired allergic contact hypersensitivity (CHS) response against trinitrochlorobenzene, which is accompanied by a reduced ability to attract dendritic cells (DCs) from the periphery into draining lymph nodes. 10 DCs are the most potent antigen-presenting cells (APCs). Their function and polarizing capacities are decisive for the outcome of Th-mediated immunity. [11][12][13] Although, it is known that OPN plays a central role for the initiation of Th1-mediated immune responses, it is unknown whether it is involved in DC instruction to induce Th1-mediated responses. In their immature state, DCs are situated in peripheral nonlymphoid tissues. 14,15 For example, Langerhans cells (LCs) are located in the epidermis. Upon stimulation, LCs/DCs undergo a maturation process resulting in the downregulation of their antigen uptake and processing capacity; upregulation of major histocompatibility complex (MHC) II and costimulatory molecules; and a switch in their expression pattern of chemokines and adhesion molecules. 14,15 As a consequence of this reprogramming, DCs migrate into lymphoid organs. 16,17 In the T-cell zone of lymph nodes, they function as APCs, which prime naive antigen-specific T cells and drive their differentiation toward Th1, Th2, or regulatory T cells. [11][12][13] The initial activation stimulus in concert with tissue environmental factors encountered by migrating DCs instruct DCs to polarize toward a phenotype that initiates Th1, Th2, or regulatory T effector cells. 11,12,18,19 Numerous viral and microbial factors, among them lipopolysaccharide (LPS), Staphylococcus aureus Cowan strain I, bacterial DNA and dsRNA, [20][21][22][23][24] and Pertussis toxin in the context of IL-1␤ and tumor necrosis factor ␣ (TNF-␣), 25 have been described as IL-12-and Th1-prompting factors. In contrast, substances that increase intracellular cyclic adenosine monophosphate (cAMP), such as cholera toxin 26 For personal use only. on May 9, 2018. by guest www.bloodjournal.org From Incomplete knowledge exists regarding tissue factors that are encountered by DCs on their w...