Naturally occurring short splice variant of CYLD positively regulates dendritic cell function.

Deubiquitination of NF-kappaB members by CYLD is crucial in controlling the magnitude and nature of cell activation. The role of the naturally occurring CYLD splice variant in dendritic cell (DC) function was analyzed using CYLD(ex7/8) mice, which lack the full-length CYLD (flCYLD) transcript and overexpress the short splice variant (sCYLD). Bone marrow-derived DCs from CYLD(ex7/8) mice display a hyperactive phenotype in vitro and in vivo and have a defect in establishing tolerance with the use of DEC-205-mediated antigen targeting to resting DCs. The combination of sCYLD overexpression and lack of flCYLD in CYLD(ex7/8) DCs leads to enhanced NF-kappaB activity accompanied by an increased nuclear translocation of the IkappaB molecule Bcl-3, along with nuclear p50 and p65. This suggests that, in contrast to flCYLD, sCYLD is a positive regulator of NF-kappaB activity, and its overexpression induces a hyperactive phenotype in DCs.

Expression of B-cell activating factor enhances protective immunity of a vaccine against Pseudomonas aeruginosa.

B-cell activating factor (BAFF), a member of the TNF family, is a potent cytokine with stimulatory effects on B and T cells. To evaluate the potential of transient overexpression of BAFF to enhance vaccine immunogenicity, a replication-deficient adenovirus expressing full-length murine BAFF (AdBAFF) was tested in a mouse vaccine model against Pseudomonas aeruginosa. When coadministered with heat-killed P. aeruginosa, AdBAFF mediated a significant increase in anti-P. aeruginosa-specific serum and lung mucosal antibodies and resulted in improved protection against a lethal respiratory challenge with P. aeruginosa. This effect was independent of the site of administration of AdBAFF and was observed both when AdBAFF was given simultaneously with heat-killed P. aeruginosa as well as when AdBAFF was administered 4 weeks after immunization with heat-killed P. aeruginosa. These data demonstrate that a temporal increase in systemic BAFF levels is able to augment a P. aeruginosa-specific immune response upon immunization with heat-killed P. aeruginosa, suggesting that the immune-stimulatory effects of BAFF may be exploited as a molecular adjuvant for genetic vaccines.

Influence of the cystic fibrosis transmembrane conductance regulator on expression of lipid metabolism-related genes in dendritic cells.

BACKGROUND: Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Infections of the respiratory tract are a hallmark in CF. The host immune responses in CF are not adequate to eradicate pathogens, such as P. aeruginosa. Dendritic cells (DC) are crucial in initiation and regulation of immune responses. Changes in DC function could contribute to abnormal immune responses on multiple levels. The role of DC in CF lung disease remains unknown. METHODS: This study investigated the expression of CFTR gene in bone marrow-derived DC. We compared the differentiation and maturation profile of DC from CF and wild type (WT) mice. We analyzed the gene expression levels in DC from naive CF and WT mice or following P. aeruginosa infection. RESULTS: CFTR is expressed in DC with lower level compared to lung tissue. DC from CF mice showed a delayed in the early phase of differentiation. Gene expression analysis in DC generated from naive CF and WT mice revealed decreased expression of Caveolin-1 (Cav1), a membrane lipid raft protein, in the CF DC compared to WT DC. Consistently, protein and activity levels of the sterol regulatory element binding protein (SREBP), a negative regulator of Cav1 expression, were increased in CF DC. Following exposure to P. aeruginosa, expression of 3beta-hydroxysterol-Delta7 reductase (Dhcr7) and stearoyl-CoA desaturase 2 (Scd2), two enzymes involved in the lipid metabolism that are also regulated by SREBP, was less decreased in the CF DC compared to WT DC. CONCLUSION: These results suggest that CFTR dysfunction in DC affects factors involved in membrane structure and lipid-metabolism, which may contribute to the abnormal inflammatory and immune response characteristic of CF.

Vaccination recommendations for Germany.

BACKGROUND: Vaccination is an effective means of preventing infectious diseases. In Germany, the Standing Vaccination Committee at the Robert Koch Institute (Ständige Impfkommission, STIKO) issues recommendations on vaccination to prevent the occurrence and spread of infectious diseases in the nation's population. METHODS: Selective literature review, including consideration of the current STIKO recommendations. RESULTS: The annually updated vaccination calendar currently includes recommendations for vaccination against diphtheria, tetanus, pertussis, type b Haemophilus influenzae, hepatitis B, poliomyelitis, and pneumococci, beginning at the age of eight weeks. From the age of twelve months onward, children should be vaccinated against measles, mumps, rubella, varicella, and serogroup C meningococci. In later childhood and adolescence, booster vaccinations are recommended, in addition to the provision of any vaccinations that may have been missed. Girls aged 12 to 17 years should be vaccinated against human papilloma virus. Adults should have their tetanus and diphtheria vaccinations refreshed regularly, and their pertussis vaccination refreshed once; from age 60 onward, they should be vaccinated against pneumococci and influenza. CONCLUSIONS: The vaccinations recommended by the STIKO are available to all German citizens free of charge and provide effective protection against infectious disease.

IL-22 is produced by innate lymphoid cells and limits inflammation in allergic airway disease.

Interleukin (IL)-22 is an effector cytokine, which acts primarily on epithelial cells in the skin, gut, liver and lung. Both pro- and anti-inflammatory properties have been reported for IL-22 depending on the tissue and disease model. In a murine model of allergic airway inflammation, we found that IL-22 is predominantly produced by innate lymphoid cells in the inflamed lungs, rather than TH cells. To determine the impact of IL-22 on airway inflammation, we used allergen-sensitized IL-22-deficient mice and found that they suffer from significantly higher airway hyperreactivity upon airway challenge. IL-22-deficiency led to increased eosinophil infiltration lymphocyte invasion and production of CCL17 (TARC), IL-5 and IL-13 in the lung. Mice treated with IL-22 before antigen challenge displayed reduced expression of CCL17 and IL-13 and significant amelioration of airway constriction and inflammation. We conclude that innate IL-22 limits airway inflammation, tissue damage and clinical decline in allergic lung disease.

Signaling pathways of the TREM-1- and TLR4-mediated neutrophil oxidative burst.

The triggering receptor expressed on myeloid cells 1 (TREM-1) is involved in the innate inflammatory response to microbial infections. Activation and expression of TREM-1 by polymorphonuclear neutrophils (PMN) occurs in concert with Toll-like receptors (TLR) such as TLR4 for bacterial lipopolysaccharide. However, it is currently unclear how this is mediated on a molecular level. Using pharmacological inhibitors and Western blot analysis we demonstrate that phosphatidyl inositide 3-kinase, phospholipase C and the mitogen-activated kinase p38MAPK are essential for the TREM-1- and TLR4-induced oxidative burst of human PMN. The activation of protein kinase B and extracellular signal-related kinase show characteristic phosphorylation patterns upon single or co-ligation indicating individual activation pathways of both receptors. Taken together, we provide new insights into the mechanisms how TREM-1 and TLR interact creating synergistic activation in PMN. These results shed a new light on our understanding of how the innate inflammatory responses are regulated and might contribute to the development of future concepts for the treatment of severe inflammatory conditions such as sepsis.

Mast cells are crucial for early inflammation, migration of Langerhans cells, and CTL responses following topical application of TLR7 ligand in mice.

Until recently, IgE-activated mast cells have been regarded merely as effector cells of adaptive immune responses, involved in allergic reactions and mucosal immunity to parasites. Herein, we report that murine dermal mast cells, activated by local administration of a cream containing the synthetic TLR7 ligand imiquimod, are essential to initiate an early inflammatory reaction. The mast-cell-derived cytokines TNF-alpha and IL-1beta play an important role in this process. Furthermore, TLR7-activated mast cells are also able to promote the emigration of Langerhans cells, which partly depends on the expression of mast-cell-derived IL-1beta. We have previously shown that TLR7 ligation enhances transcutaneous immunization evoked by topical application of vaccine antigens to the skin, a procedure that directly targets skin-resident antigen-presenting cells. Consequently, we now demonstrate here that the capacity to mount a peptide-specific cytotoxic T-lymphocyte response following transcutaneous immunization using imiquimod as adjuvant is severely impaired in mast-cell-deficient mice. Thus, these findings demonstrate the potent versatility of alternatively activated mast cells at the interface of innate and adaptive immunity.

Specific and redundant roles for NFAT transcription factors in the expression of mast cell-derived cytokines.

By virtue of their ability to express a plethora of biologically highly active mediators, mast cells (MC) are involved in both adaptive and innate immune responses. MC-derived Th2-type cytokines are thought to act as local amplifiers of Th2 reactions, including chronic inflammatory disorders such as allergic asthma, whereas MC-derived TNF-alpha is a critical initiator of antimicrobial defense. In this study, we demonstrate that the transcription factors NFATc1 and NFATc2 are part of a MC-specific signaling network that regulates the expression of TNF-alpha and IL-13, whereas NFATc3 is dispensable. Primary murine bone marrow-derived MC from NFATc2(-/-) mice, activated by either ionomycin or IgE/Ag cross-link, display a strong reduction in the production of these cytokines, compared with bone marrow-derived MC from wild-type mice. Detailed analyses of TNF-alpha and IL-13 expression using small interfering RNA-mediated knockdown reveals that both NFATc2 and NFATc1 are able to drive the expression of these cytokines, whereas neither degranulation nor the expression of IL-6 depends on NFAT activity. These results support the view that high NFAT activity is necessary for TNF-alpha and IL-13 promoter induction in MC, irrespective of whether NFATc2 or NFATc1 or a combination of both is present.

CCR4-deficient mice show prolonged graft survival in a chronic cardiac transplant rejection model.

Chronic graft rejection mediated by cellular immune responses still poses a serious clinical problem in transplant surgery. Chemokines coordinate the recruitment of leukocytes in inflammatory and immune responses. Their precise functions in the rejection of allografts are still ill defined. This study investigates the role of chemokine receptor 4 (CCR4) in acute and chronic cardiac allograft rejection in mice. Allogeneic hearts were transplanted into CCR4 deficient (CCR4(-/-)) and control recipients. Reverse transcription-PCR showed transcription of macrophage-derived chemokine and thymus and activation-regulated chemokine, the cognate chemokine ligands of CCR4, within the graft. Compared to wild-type controls, acute allograft rejection in CCR4(-/-) recipients was only slightly prolonged. In contrast, in a gallium nitrate chronic cardiac allograft rejection model, cardiac graft survival was significantly prolonged in CCR4(-/-) recipients. A relative increase in the percentage of graft infiltrating CD8(+) T cells in CCR4(-/-) recipients was observed 30 days after transplantation and was accompanied by a decrease in CD4(+) T cells. Moreover, the percentage of NK1.1(+)CD3(+) graft-infiltrating cells was significantly reduced on day 5 and day 30 post transplantation. These findings indicate that CCR4 is involved in the recruitment of NK1.1(+)CD3(+) cells into cardiac allografts and clearly establish an important and novel role for CCR4 in chronic graft rejection.

A Cre-inducible diphtheria toxin receptor mediates cell lineage ablation after toxin administration.

A new system for lineage ablation is based on transgenic expression of a diphtheria toxin receptor (DTR) in mouse cells and application of diphtheria toxin (DT). To streamline this approach, we generated Cre-inducible DTR transgenic mice (iDTR) in which Cre-mediated excision of a STOP cassette renders cells sensitive to DT. We tested the iDTR strain by crossing to the T cell- and B cell-specific CD4-Cre and CD19-Cre strains, respectively, and observed efficient ablation of T and B cells after exposure to DT. In MOGi-Cre/iDTR double transgenic mice expressing Cre recombinase in oligodendrocytes, we observed myelin loss after intraperitoneal DT injections. Thus, DT crosses the blood-brain barrier and promotes cell ablation in the central nervous system. Notably, we show that the developing DT-specific antibody response is weak and not neutralizing, and thus does not impede the efficacy of DT. Our results validate the use of iDTR mice as a tool for cell ablation in vivo.

The lymphotoxin beta receptor is critically involved in controlling infections with the intracellular pathogens Mycobacterium tuberculosis and Listeria monocytogenes.

Containment of intracellularly viable microorganisms requires an intricate cooperation between macrophages and T cells, the most potent mediators known to date being IFN-gamma and TNF. To identify novel mechanisms involved in combating intracellular infections, experiments were performed in mice with selective defects in the lymphotoxin (LT)/LT beta R pathway. When mice deficient in LT alpha or LT beta were challenged intranasally with Mycobacterium tuberculosis, they showed a significant increase in bacterial loads in lungs and livers compared with wild-type mice, suggesting a role for LT alpha beta heterotrimers in resistance to infection. Indeed, mice deficient in the receptor for LT alpha(1)beta(2) heterotrimers (LT beta R-knockout (KO) mice) also had significantly higher numbers of M. tuberculosis in infected lungs and exhibited widespread pulmonary necrosis already by day 35 after intranasal infection. Furthermore, LT beta R-KO mice were dramatically more susceptible than wild-type mice to i.p. infection with Listeria monocytogenes. Compared with wild-type mice, LT beta R-KO mice had similar transcript levels of TNF and IFN-gamma and recruited similar numbers of CD3(+) T cells inside granulomatous lesions in M. tuberculosis-infected lungs. Flow cytometry revealed that the LT beta R is expressed on pulmonary macrophages obtained after digestion of M. tuberculosis-infected lungs. LT beta R-KO mice showed delayed expression of inducible NO synthase protein in granuloma macrophages, implicating deficient macrophage activation as the most likely cause for enhanced susceptibility of these mice to intracellular infections. Since LIGHT-KO mice proved to be equally resistant to M. tuberculosis infection as wild-type mice, these data demonstrate that signaling of LT alpha(1)beta(2) heterotrimers via the LT beta R is an essential prerequisite for containment of intracellular pathogens.