Lipopolysaccharide (LPS) from Gram-negative bacteria is one of the most potent innate immune-activating stimuli known. Here we review the current understanding of LPS effects on human monocyte and macrophage function. We provide an overview of LPS signal transduction with attention given to receptor cooperativity and species differences in LPS responses, as well as the role of tyrosine phosphorylation and lysine acetylation in signalling. We also review LPS-regulated transcription, with emphasis on chromatin remodeling and primary versus secondary transcriptional control mechanisms. Finally, we review the regulation and function of LPS-inducible cytokines produced by human monocytes and macrophages including TNFα, the IL-1 family, IL-6, IL-8, the IL-10 family, the IL-12 family, IL-15 and TGFβ.

Activation of the NLRP3 inflammasome enables monocytes and macrophages to release high levels of interleukin-1β during inflammatory responses. Concentrations of extracellular calcium can increase at sites of infection, inflammation or cell activation. Here we show that increased extracellular calcium activates the NLRP3 inflammasome via stimulation of G protein-coupled calcium sensing receptors. Activation is mediated by signalling through the calcium-sensing receptor and GPRC6A via the phosphatidyl inositol/Ca2+ pathway. The resulting increase in the intracellular calcium concentration triggers inflammasome assembly and Caspase-1 activation. We identified necrotic cells as one source for excess extracellular calcium triggering this activation. In vivo, increased calcium concentrations can amplify the inflammatory response in the mouse model of carrageenan-induced footpad swelling, and this effect was inhibited in GPRC6A−/− mice. Our results demonstrate that G-protein-coupled receptors can activate the inflammasome, and indicate that increased extracellular calcium has a role as a danger signal and amplifier of inflammation.

Obesity is accompanied by a systemic chronic low-grade inflammation as well as dysfunctions of several innate and adaptive immune cells. Recent findings emphasize an impaired functionality and phenotype of natural killer (NK) cells under obese conditions. This review provides a detailed overview on research related to overweight and obesity with a particular focus on NK cells. We discuss obesity-associated alterations in subsets, distribution, phenotype, cytotoxicity, cytokine secretion, and signaling cascades of NK cells investigated in vitro as well as in animal and human studies. In addition, we provide recent insights into the effects of physical activity and obesity-associated nutritional factors as well as the reduction of body weight and fat mass on NK cell functions of obese individuals. Finally, we highlight the impact of impaired NK cell physiology on obesity-associated diseases, focusing on the elevated susceptibility for viral infections and increased risk for cancer development and impaired treatment response.NK cells are large granular lymphocytes that mediate rapid innate immunity against viruses, bacteria, parasites, and tumor cells without prior sensitization. NK cells primarily develop and mature in the bone marrow, migrate through the bloodstream, and seed into secondary lymphoid organs, like thymus, spleen, and lymph nodes as well as in other peripheral tissues, like lung, liver, kidney, uterus, and the gastrointestinal tract (23). In blood, NK cells represent 1-6% of all leukocytes and comprise up to 15% of human peripheral blood mononuclear cells (PBMCs). Human NK cells have been defined by the expression of adhesion molecule CD56 and by the absence of the T cell marker CD3. Based on their expression level of CD56 and the Fcγ receptor CD16, NK cells are subdivided into different subpopulations. The two major and classically defined subsets are the CD56 dim CD16 bright NK cells and the CD56 bright CD16 dim/neg NK cells. CD56 dim CD16 bright NK cells represent about 90% of all NK cells and are predominantly found in peripheral blood (24). They are mostly responsible for cytotoxic activity and target cell killing but are also a source of pro-inflammatory Abbreviations: ACM, adipocyte-conditioned media; Adamts3, a disintegrin-like and metallopeptidase with thrombospondin type 1 motif, 3; AdipoR, adiponectin receptor; Anxa8, annexin A8; AT, adipose tissue; Bax, Bcl-2-associated X protein; Bcl, B-cell lymphoma; BMI, body mass index; CCR, CC chemokine receptor; Csf1r, colony stimulating factor 1 receptor; CX3CR1, C-X3-C-motif chemokine receptor 1; DNAM-1, DNAX accessory molecule-1; ESR, estrogen receptor; FasL, Fas ligand; IFN-γ, interferon; GM-CSF; granulocyte macrophage colony-stimulating factor; H6pd, hexose-6-phosphate dehydrogenase; Hk2, hexokinase 2; IL, interleukinIL-6R; interleukin-6 receptor; Il18rap, interleukin 18 receptor accessory protein; IP-10, interferon gamma-induced protein 10; JAK, Janus kinase; KIR, killer immunoglobulin-like receptor; Klra1, killer lectin-like receptor subfamil...

Purpose: Cancers have developed a number of strategies to escape immune responses including the differential expression of costimulatory molecules of the B7 family. B7-H3 and B7-H4 have recently been described in different tumor entities but the relevance for melanoma has not yet been studied so far.Experimental Design: Using immunohistochemistry, B7-H3 and B7-H4 expression was studied on 29 melanoma lesions. Survival curves and log-rank tests were used to test the association of protein expression with survival. Cell lines were evaluated for B7-H3 and B7-H4 expression by PCR and flow cytometry. Functional T-cell-tumor coculture assays were carried out with in vitro generated tumor transfectants.Results: B7-H3 and B7-H4 expression was detected in primary tumor lesions (29 of 29 and 28 of 29) and in metastases (28 of 29 and 26 of 29). The numbers of CD68 þ macrophages were significantly lower in patients with low B7-H4 expression, whereas CD8 þ T-cell infiltrates were independent of expression levels.Furthermore, a survival benefit for patients with B7-H4 low expressing melanoma was found, whereas B7-H3 was not associated with any clinical parameter. All 23 melanoma cell lines analyzed expressed B7-H3 and B7-H4 mRNA and protein, but B7-H4 was restricted to intracellular compartments. On silencing of B7-H3 by specific shRNA tumor-associated antigen-specific T cell responses were unaltered. Overexpression of B7-H4 on melanoma cells did not alter the cytotoxicity of different CD8 þ effector cells, but drastically inhibited cytokine production. Conclusions: Our study provides for the first time evidence of B7-H4 expression on melanoma cells as a mechanism controlling tumor immunity which is associated with patients' survival. Clin Cancer Res; 17(10); 3100-11. Ó2011 AACR.