Adhesive interactions of leukocytes and endothelial cells initiate leukocyte migration to inflamed tissue and are important for immune surveillance. Acute and chronic inflammatory diseases show a dysregulated immune response and result in a massive efflux of leukocytes that contributes to further tissue damage. Therefore, targeting leukocyte trafficking may provide a potent form of antiinflammatory therapy. Leukocyte migration is initiated by interactions of the cell adhesion molecules E-, L-, and P-selectin and their corresponding carbohydrate ligands. Compounds that efficiently address these interactions are therefore of high therapeutic interest. Based on this rationale we investigated synthetic dendritic polyglycerol sulfates (dPGS) as macromolecular inhibitors that operate via a multivalent binding mechanism mimicking naturally occurring ligands. dPGS inhibited both leukocytic L-selectin and endothelial P-selectin with high efficacy. Size and degree of sulfation of the polymer core determined selectin binding affinity. Administration of dPGS in a contact dermatitis mouse model dampened leukocyte extravasation as effectively as glucocorticoids did and edema formation was significantly reduced. In addition, dPGS interacted with the complement factors C3 and C5 as was shown in vitro and reduced C5a levels in a mouse model of complement activation. Thus, dPGS represent an innovative class of a fully synthetic polymer therapeutics that may be used for the treatment of inflammatory diseases.anti-inflammatory drug | complement inhibition | multiple target binding | multivalent selectin inhibitor | synthetic polymer

Elevated IL-10 has been implicated in reactivation tuberculosis (TB). Since macrophages rather than T cells were reported to be the major source of IL-10 in TB, we analyzed the consequences of a macrophage-specific overexpression of IL-10 in transgenic mice (macIL-10-transgenic) after aerosol infection with Mycobacterium tuberculosis (Mtb). MacIL-10 transgenic mice were more susceptible to chronic Mtb infection than nontransgenic littermates, exhibiting higher bacterial loads in the lung after 12 wk of infection and dying significantly earlier than controls. The differentiation, recruitment, and activation of Th1 cells as well as the induction of IFN-γ-dependent effector genes against Mtb were not affected by macrophage-derived IL-10. However, microarray analysis of pulmonary gene expression revealed patterns characteristic of alternative macrophage activation that were overrepresented in Mtb-infected macIL-10 transgenic mice. Importantly, arginase-1 gene expression and activity were strikingly enhanced in transgenic mice accompanied by a reduced production of reactive nitrogen intermediates. Moreover, IL-10-dependent arginase-1 induction diminished antimycobacterial effector mechanisms in macrophages. Taken together, macrophage-derived IL-10 triggers aspects of alternative macrophage activation and promotes Mtb recrudescence independent of overt effects on anti-TB T cell immunity.

CD8 + T cells are involved in protection againstMycobacterium tuberculosis infection and represent a promising target for new vaccine strategies. Because IL-15 is important for the homeostasis of CD8 + T cells, we studied the immune response in IL-15-deficient mice during tuberculosis. In the absence of IL-15, CD8 + T cells failed to efficiently accumulate in draining lymph nodes and at the site of infection. The expression of antigen-specific effector functions, such as the production of interferon-c and cytotoxicity, were impaired in CD8 + T cells, but not CD4 + T cells, from IL-15-deficient mice. This defect was associated with an increased mortality of IL-15-deficient mice during the chronic phase of infection. The lectin-like stimulatory receptor natural killer group 2D (NKG2D) was up-regulated on CD8 + T cells only from wild-type mice, but not from IL-15-deficient mice. Mechanistically, blocking NKG2D function with an mAb inhibited M. tuberculosis-directed CD8 + T cell responses in vitro. We conclude that in addition to regulating the expansion of CD8 + T cells, IL-15 is also necessary for inducing effector mechanisms in CD8 + T cells that depend on NKG2D expression. Hence, our results implicate IL-15 and NKG2D as promising targets for modulating CD8 + T cellmediated protection against tuberculosis. IntroductionHuman tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) is responsible for eight million new cases and two million deaths annually [1]. Improved vaccination strategies will need to target all mechanisms that contribute to restricting the growth of Mtb [2]. Although the cell-mediated immune response is known to be critical in host defense against infection with mycobacteria, the relative contribution of T cell subsets and the mechanisms by which T cells participate in the control of infection are still not completely defined. It is generally accepted that both, CD4 + and CD8 + T cells, are an essential component of protective immunity against TB [3]. CD4 + T cells are particularly critical during the early phase of infection, while CD8 + T cells appear to contribute mostly at later stages [4,5]. Both, CD4 + and CD8 + T cells, produce interferon-c (IFN-c) which in turn stimulates the anti-microbial activity of macrophages. Intracellular pathogens are then killed through reactive nitrogen intermediates produced by the inducible nitric oxide synthase [6] or through effector mechanisms mediated by the newly described member of the 47-kD guanosine triphosphatase family, . CD8 + T cells can also cause death of both target cells and their intracellular bacterial cargo, either through perforin-dependent cytolysis by the release of granzymes and granulysin, or by ligation of Fas ligand (FasL) on their surface with Fas on infected macrophages [5,[8][9][10]. Because CD8 + T cells are involved in protection during the chronic stage of TB [4,5,11], and participate in memory immune responses to Mtb infection [12], generating a more robust CD8 + T cell response may provide an effective vaccination strate...

T-cell-mediated processes play an essential role in the pathogenesis of several inflammatory skin diseases such as atopic dermatitis, allergic contact dermatitis and psoriasis. The aim of this study was to investigate the role of the IL-2-inducible tyrosine kinase (Itk), an enzyme acting downstream of the T-cell receptor (TCR), in T-cell-dependent skin inflammation using three approaches. Itk knockout mice display significantly reduced inflammatory symptoms in mouse models of acute and subacute contact hypersensitivity (CHS) reactions. Systemic administration of a novel small molecule Itk inhibitor, Compound 44, created by chemical optimization of an initial high-throughput screening hit, inhibited Itk's activity with an IC50 in the nanomolar range. Compound 44 substantially reduced proinflammatory immune responses in vitro and in vivo after systemic administration in two acute CHS models. In addition, our data reveal that human Itk, comparable to its murine homologue, is expressed mainly in T cells and is increased in lesional skin from patients with atopic dermatitis and allergic contact dermatitis. Finally, silencing of Itk by RNA interference in primary human T cells efficiently blocks TCR-induced lymphokine secretion. In conclusion, Itk represents an interesting new target for the therapy of T-cell-mediated inflammatory skin diseases.

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