Altered expression of autoimmune regulator in infant down syndrome thymus, a possible contributor to an autoimmune phenotype.

Down syndrome (DS), caused by trisomy of chromosome 21, is associated with immunological dysfunctions such as increased frequency of infections and autoimmune diseases. Patients with DS share clinical features, such as autoimmune manifestations and specific autoantibodies, with patients affected by autoimmune polyendocrine syndrome type 1. Autoimmune polyendocrine syndrome type 1 is caused by mutations in the autoimmune regulator (AIRE) gene, located on chromosome 21, which regulates the expression of tissue-restricted Ags (TRAs) in thymic epithelial cells. We investigated the expression of AIRE and TRAs in DS and control thymic tissue using quantitative PCR. AIRE mRNA levels were elevated in thymic tissue from DS patients, and trends toward increased expression of the AIRE-controlled genes INSULIN and CHRNA1 were found. Immunohistochemical stainings showed altered cell composition and architecture of the thymic medulla in DS individuals with increased frequencies of AIRE-positive medullary epithelial cells and CD11c-positive dendritic cells as well as enlarged Hassall's corpuscles. In addition, we evaluated the proteomic profile of thymic exosomes in DS individuals and controls. DS exosomes carried a broader protein pool and also a larger pool of unique TRAs compared with control exosomes. In conclusion, the increased AIRE gene dose in DS could contribute to an autoimmune phenotype through multiple AIRE-mediated effects on homeostasis and function of thymic epithelial cells that affect thymic selection processes.

Human thymic epithelial primary cells produce exosomes carrying tissue-restricted antigens.

Exosomes are nano-sized vesicles released by cells into the extracellular space and have been shown to be present in thymic tissue both in mice and in humans. The source of thymic exosomes is however still an enigma and hence it is not known whether thymic epithelial cells (TECs) are able to produce exosomes. In this work, we have cultured human TECs and isolated exosomes. These exosomes carry tissue-restricted antigens (TRAs), for example, myelin basic protein and desmoglein 3. The presence of TRAs indicates a possible role for thymic epithelium-derived exosomes in the selection process of thymocytes. The key contribution of these exosomes could be to disseminate self-antigens from the thymic epithelia, thus making them more accessible to the pool of maturing thymocytes. This would increase the coverage of TRAs within the thymus, and facilitate the process of positive and negative selection.

Resonant inelastic scattering spectra of free molecules with vibrational resolution.

Inelastic x-ray scattering spectra excited at the 1s(-1)π* resonance of gas phase O2 have been recorded with an overall energy resolution that allows for well-resolved vibrational progressions. The nuclear wave packet dynamics in the intermediate state is reflected in vibrational excitations of the electronic ground state, and by fine-tuning the excitation energy the dissociation dynamics in the predissociative B'(3)Πg final state is controlled.

Gender dependent importance of IRAK-1 in dextran sulfate sodium induced colitis.

Toll-like receptor (TLR) signaling is important for the induction of pro-inflammatory cytokines and interferon (IFN)-inducible genes in response to bacterial and viral challenge. Interleukin-1 receptor-associated kinase-1 (IRAK-1) is a signaling kinase situated downstream of the adapter protein myeloid differentiation factor 88 (MyD88) in the TLR intracellular signaling cascade and is required for normal signal transduction through this pathway. We investigated the importance of IRAK-1 in intestinal inflammation by using the dextran sulfate sodium (DSS)-colitis model. We show that IRAK-1 deficient mice are protected against systemic signs of inflammation, i.e., weight loss and spleen enlargement compared to wild-type controls irrespective of gender. However, IRAK-1(-/y) males but not IRAK-1(-/-) females display significant protection against colitis and thymic atrophy compared to wild-type mice. Our results indicate a gender specific effect of IRAK-1 in the DSS-induced colitis, an interesting finding since the Irak-1 gene is located on the X-chromosome and several inflammatory diseases have a gender dependent incidence.

Thymic exosomes promote the final maturation of thymocytes.

Extensive knowledge has been gained the last years concerning mechanisms underlying the selection of single positive thymocytes in the thymic medulla. Less is known regarding other important processes in the thymic medulla such as the regulation of late stage thymocyte maturation. We have previously reported that exosomes are abundant in the thymus with a phenotype that indicates an epithelial cell origin and immunoregulatory properties. In this study we use an in vitro system to investigate the effects of thymic exosomes on the maturation of single positive thymocytes as well as effects on nTreg formation. We show that thymic exosomes promote the maturation of single positive CD4+CD25- cells into mature thymocytes with S1P1+Qa2+ and CCR7+Qa2+ phenotypes. Furthermore, we show that thymic exosomes reduce the formation of CD4+CD25+FoxP3+ thymocytes and that these exosome effects are independent of dendritic cell co-stimulation but require intact exosomal RNA content and surface proteins. An efficient direct uptake of exosomes by both thymocytes and thymic DC's is also demonstrated. In conclusion, this study demonstrates that exosomes may represent a new route of communication within the thymus.

Improved Estimation of Human Lipoprotein Kinetics with Mixed Effects Models.

CONTEXT: Mathematical models may help the analysis of biological systems by providing estimates of otherwise un-measurable quantities such as concentrations and fluxes. The variability in such systems makes it difficult to translate individual characteristics to group behavior. Mixed effects models offer a tool to simultaneously assess individual and population behavior from experimental data. Lipoproteins and plasma lipids are key mediators for cardiovascular disease in metabolic disorders such as diabetes mellitus type 2. By the use of mathematical models and tracer experiments fluxes and production rates of lipoproteins may be estimated. RESULTS: We developed a mixed effects model to study lipoprotein kinetics in a data set of 15 healthy individuals and 15 patients with type 2 diabetes. We compare the traditional and the mixed effects approach in terms of group estimates at various sample and data set sizes. CONCLUSION: We conclude that the mixed effects approach provided better estimates using the full data set as well as with both sparse and truncated data sets. Sample size estimates showed that to compare lipoprotein secretion the mixed effects approach needed almost half the sample size as the traditional method.

Investigations of a compartmental model for leucine kinetics using non-linear mixed effects models with ordinary and stochastic differential equations.

Non-linear mixed effects (NLME) models represent a powerful tool to simultaneously analyse data from several individuals. In this study, a compartmental model of leucine kinetics is examined and extended with a stochastic differential equation to model non-steady-state concentrations of free leucine in the plasma. Data obtained from tracer/tracee experiments for a group of healthy control individuals and a group of individuals suffering from diabetes mellitus type 2 are analysed. We find that the interindividual variation of the model parameters is much smaller for the NLME models, compared to traditional estimates obtained from each individual separately. Using the mixed effects approach, the population parameters are estimated well also when only half of the data are used for each individual. For a typical individual, the amount of free leucine is predicted to vary with a standard deviation of 8.9% around a mean value during the experiment. Moreover, leucine degradation and protein uptake of leucine is smaller, proteolysis larger and the amount of free leucine in the body is much larger for the diabetic individuals than the control individuals. In conclusion, NLME models offers improved estimates for model parameters in complex models based on tracer/tracee data and may be a suitable tool to reduce data sampling in clinical studies.

IL-1 receptor-associated kinase M downregulates DSS-induced colitis.

BACKGROUND: Ulcerative colitis is associated with increased colon permeability resulting in bacterial translocation into the lamina propria. We investigate the importance of the Toll-like receptor (TLR) regulating protein IL-1 receptor-associated kinase M (IRAK-M) using the erosive dextran sulfate sodium (DSS)-induced model of colitis. METHODS: IRAK-M-competent and -incompetent mice were treated with 3% DSS for 5 days followed by 2 days of regular drinking water. Clinical signs of disease were followed for 7 days. At day 7 the mice were sacrificed and plasma and tissue were collected for histopathological examination and analyses of the production of cytokines and chemokines as well as expression of T-cell transcription factors. RESULTS: At day 7 IRAK-M-deficient mice display a reduced total body weight (77.1 ± 2.1 versus 88.5 ± 2.0, *P = 0.002) and an increased macroscopical (2.7 ± 0.2 versus 1.6 ± 0.1, *P = 0.002) and histopathological (6.0 ± 0 versus 3.3 ± 0.5, *P = < 0.001) colon score compared to wildtype mice. Furthermore, IRAK-M-deficient mice have increased colon mRNA expression of proinflammatory cytokines and increased tumor necrosis factor concentrations (41.1 ± 13.5 versus 12.8 ± 2.0 pg/mL, *P = 0.010) in plasma. CONCLUSIONS: This is the first report examining the role of IRAK-M in colitis. We find that IRAK-M is of critical importance in downregulating induction and progression of DSS colitis, and thereby suggesting that IRAK-M might be a target for future interventional therapies.