Cells release into the extracellular environment diverse types of membrane vesicles of endosomal and plasma membrane origin called exosomes and microvesicles, respectively. These extracellular vesicles (EVs) represent an important mode of intercellular communication by serving as vehicles for transfer between cells of membrane and cytosolic proteins, lipids, and RNA. Deficiencies in our knowledge of the molecular mechanisms for EV formation and lack of methods to interfere with the packaging of cargo or with vesicle release, however, still hamper identification of their physiological relevance in vivo. In this review, we focus on the characterization of EVs and on currently proposed mechanisms for their formation, targeting, and function.

https://rupress.org/jcb/article-pdf/200/4/373/1262520/jcb_201211138.pdf

Extracellular vesicles: exosomes, microvesicles, and friends.

The classical pathway of interferon-gamma-dependent activation of macrophages by T helper 1 (T(H)1)-type responses is a well-established feature of cellular immunity to infection with intracellular pathogens, such as Mycobacterium tuberculosis and HIV. The concept of an alternative pathway of macrophage activation by the T(H)2-type cytokines interleukin-4 (IL-4) and IL-13 has gained credence in the past decade, to account for a distinctive macrophage phenotype that is consistent with a different role in humoral immunity and repair. In this review, I assess the evidence in favour of alternative macrophage activation in the light of macrophage heterogeneity, and define its limits and relevance to a range of immune and inflammatory conditions.

Alternative activation of macrophages

It is not yet known whether DNA methylation levels can be used to accurately predict age across a broad spectrum of human tissues and cell types, nor whether the resulting age prediction is a biologically meaningful measure. I developed a multi-tissue predictor of age that allows one to estimate the DNA methylation age of most tissues and cell types. The predictor, which is freely available, was developed using 8,000 samples from 82 Illumina DNA methylation array datasets, encompassing 51 healthy tissues and cell types. I found that DNA methylation age has the following properties: first, it is close to zero for embryonic and induced pluripotent stem cells; second, it correlates with cell passage number; third, it gives rise to a highly heritable measure of age acceleration; and, fourth, it is applicable to chimpanzee tissues. Analysis of 6,000 cancer samples from 32 datasets showed that all of the considered 20 cancer types exhibit significant age acceleration, with an average of 36 years. Low age-acceleration of cancer tissue is associated with a high number of somatic mutations and TP53 mutations, while mutations in steroid receptors greatly accelerate DNA methylation age in breast cancer. Finally, I characterize the 353 CpG sites that together form an aging clock in terms of chromatin states and tissue variance. I propose that DNA methylation age measures the cumulative effect of an epigenetic maintenance system. This novel epigenetic clock can be used to address a host of questions in developmental biology, cancer and aging research.

/pdf/dna-methylation-age-of-human-tissues-and-cell-types-528gzlrlkl.pdf

DNA methylation age of human tissues and cell types

Allergic rhinitis is a symptomatic disorder of the nose induced after allergen exposure by an IgE-mediated inflammation of the membranes lining the nose. It is a global health problem that causes major illness and disability worldwide. Over 600 million patients from all countries, all ethnic groups and of all ages suffer from allergic rhinitis. It affects social life, sleep, school and work and its economic impact is substantial. Risk factors for allergic rhinitis are well identified. Indoor and outdoor allergens as well as occupational agents cause rhinitis and other allergic diseases. The role of indoor and outdoor pollution is probably very important, but has yet to be fully understood both for the occurrence of the disease and its manifestations.

In 1999, during the Allergic Rhinitis and its Impact on Asthma (ARIA) WHO workshop, the expert panel proposed a new classification for allergic rhinitis which was subdivided into 'intermittent' or 'persistent' disease.

This classification is now validated. The diagnosis of allergic rhinitis is often quite easy, but in some cases it may cause problems and many patients are still under-diagnosed, often because they do not perceive the symptoms of rhinitis as a disease impairing their social life, school and work.

The management of allergic rhinitis is well established and the ARIA expert panel based its recommendations on evidence using an extensive review of the literature available up to December 1999. The statements of evidence for the development of these guidelines followed WHO rules and were based on those of Shekelle et al. A large number of papers have been published since 2000 and are extensively reviewed in the 2008 Update using the same evidence-based system. Recommendations for the management of allergic rhinitis are similar in both the ARIA workshop report and the 2008 Update. In the future, the GRADE approach will be used, but is not yet available.

Another important aspect of the ARIA guidelines was to consider co-morbidities. Both allergic rhinitis and asthma are systemic inflammatory conditions and often co-exist in the same patients. In the 2008 Update, these links have been confirmed.

The ARIA document is not intended to be a standard-of-care document for individual countries. It is provided as a basis for physicians, health care professionals and organizations involved in the treatment of allergic rhinitis and asthma in various countries to facilitate the development of relevant local standard-of-care documents for patients.

/pdf/allergic-rhinitis-and-its-impact-on-asthma-aria-2008-update-13eqfzaw4u.pdf

Allergic rhinitis and its impact on asthma (ARIA) 2008 update (in collaboration with the World Health Organization, GA(2)LEN and AllerGen)

The study of extracellular vesicles (EVs) has the potential to identify unknown cellular and molecular mechanisms in intercellular communication and in organ homeostasis and disease. Exosomes, with an average diameter of ~100 nanometers, are a subset of EVs. The biogenesis of exosomes involves their origin in endosomes, and subsequent interactions with other intracellular vesicles and organelles generate the final content of the exosomes. Their diverse constituents include nucleic acids, proteins, lipids, amino acids, and metabolites, which can reflect their cell of origin. In various diseases, exosomes offer a window into altered cellular or tissue states, and their detection in biological fluids potentially offers a multicomponent diagnostic readout. The efficient exchange of cellular components through exosomes can inform their applied use in designing exosome-based therapeutics.

The biology, function, and biomedical applications of exosomes

In several conditions in the skin, characterized by T-cell infiltration, keratinocytes are induced to synthesize and express class II transplantation antigens. The biological significance of this induced expression is still not understood. In this study, class II antigens were induced on rat ear keratinocytes by local intradermal injections into the ear of rat recombinant interferon-gamma (IFN-gamma). Epidermal cell suspensions prepared from these ears contained more than 50% class II-expressing cells, as judged by immunocytochemistry, compared with less than 5% in untreated epidermis. When comparing the capacity of these to different epidermal cell populations to stimulate a syngeneic PPD-specific T-helper cell line, it was found that IFN-gamma-exposed epidermal cells induced a lower T-cell response to PPD than did normal epidermal cells. This discrepancy could not be explained by either an infiltration of inflammatory cells into the epidermis of IFN-gamma-treated ears or by a difference in interleukin-1 production as determined in culture supernatants. The addition of indomethacin to cultures with IFN-gamma-exposed epidermal cells restored the T-cell response to PPD to that of normal epidermal cells, suggesting an inhibitory effect of prostaglandins. Our data indicate that epidermal cells exposed to IFN-gamma in vivo can suppress an antigen-specific T-cell proliferation.

Effects on rat T-helper cell proliferation by syngeneic epidermal cells exposed to IFN-gamma in vivo.

The phenotypes of infiltrating cells and class II transplantation antigens on keratinocytes in candida and dermatophyte lesions from 15 patients were analysed in situ with an immunohistochemical double staining technique combined with periodic acid-Schiff staining. In five out of ten biopsies from candida lesions and in one of five biopsies from dermatophyte lesions the keratinocytes expressed HLA-DR but not HLA-DQ antigens. The HLA-DR expression was patchy in all and most pronounced in two candida biopsies which also contained large infiltrates of anti-Leu 3a reactive T lymphocytes. The induction of detectable amounts of different class II antigens on keratinocytes might depend on the type of antigen, the magnitude and duration of the response elicited and/or the immunological state of the patient.

Fungal infections inducing HLA-DR but not HLA-DQ transplantation antigens on keratinocytes.

Exposure to sawdust and its contaminants, e.g., terpenes, may cause respiratory tract and lung parenchymal inflammation. To monitor these changes over time, Sprague-Dawley rats were exposed at one occasion to 2.5 mg sawdust or saline by intratracheal instillation. Flow cytometry analyses were done on bronchoalveolar lavage (BAL) cells. Lung tissue specimens were analyzed histologically and immunohistochemically. After one week, the number of BAL polymorphonuclear leukocytes was increased (P<0.05,N=8), followed at six weeks by increases of macrophages and lymphocytes (bothP<0.01,N=8). Enhanced expressions of class II antigens and complement receptors on macrophages after one week were even more pronounced at six weeks, indicating cellular activation. The BAL findings, also including increased (P<0.001,N=8) concentrations of hyaluronan with progressing changes over time, confirmed the signs of inflammation, as did the histological analysis of the lung tissue specimens with an accumulation of polymorphonuclears, macrophages, and hyaluronan in the interstitium.

Sawdust-induced inflammatory changes in rat lung: effects on alveolar and interstitial cells in relation to time.

Herein, a novel method to synthesize soluble, sub-micrometer sized protein aggregates is demonstrated by mixing native and denatured proteins without using bacteria and contaminating proteins. Ovalbumin (OVA) is employed as a model protein. The average size of the formed aggregates can be controlled by adjusting the fraction of denatured protein in the sample and it is possible to make unimodal size distributions of protein aggregates. OVA aggregates with a size of ∼95 nm are found to be more immunogenic compared to native OVA in a murine splenocyte proliferation assay. These results suggest that the novel method of engineering size specific sub-micrometer sized aggregates may constitute a potential route to increasing the efficacy of protein vaccines. The protein aggregates may also be promising for use in other applications including the surface functionalization of biomaterials and as industrial catalysis materials.

Nanoscale Size Control of Protein Aggregates

Background: Atopic eczema is the most common chronic, relapsing, inflammatory skin disorder with an atopic background. Previous studies have shown that IgE-mediated reactivity to self-antigens plays a role in the pathogenesis of the disease. However, the expression of self-antigens associated with atopic eczema in the lesional skin is poorly investigated.Aim of the study: This study was aimed to show that IgE-binding self antigens are over-expressed in atopic eczema lesions. Methods: Tubulin-α and HLA-DR-α, two recently described self-antigens, were stained by immunohistochemistry in skin specimens from chronic and acute atopic eczema lesions, unaffected skin from the same patients or skin from healthy controls.Results: The expression of tubulin-α and HLA-DR-α is up-regulated in atopic eczema lesions compared to nonlesional or healthy skin and correlates with the number of infiltrating immune cells and the degree of inflammation.Conclusion: Upregulation of IgE-binding self-antigens in lesional skin of atopic eczema patients might further promote the existing inflammation and induce exacerbations of the disease in the absence of exposure to environmental allergens.

https://www.longdom.org/open-access/the-ige-binding-self-antigens-tubulin-a-and-hla-dr-a-are-overexpressed-in-lesional-skin-2155-9899.1000109.pdf

Annika Scheynius

Papers

Effects on rat T-helper cell proliferation by syngeneic epidermal cells exposed to IFN-gamma in vivo.

Fungal infections inducing HLA-DR but not HLA-DQ transplantation antigens on keratinocytes.

Sawdust-induced inflammatory changes in rat lung: effects on alveolar and interstitial cells in relation to time.

Nanoscale Size Control of Protein Aggregates

The Ige-Binding Self-Antigens Tubulin-ÃÂ and HLA-DR-ÃÂ are Overexpressed in Lesional Skin of Atopic Eczema Patients