ß7 integrins are required to give rise to intestinal mononuclear phagocytes with tolerogenic potential.

BACKGROUND AND OBJECTIVE: While pro-inflammatory monocyte trafficking to the intestine has been partially characterised, the molecules required for migration of tolerogenic mononuclear phagocytes (dendritic cells (DC) and macrophages) are unknown. We hypothesised that the gut-homing receptor integrin α4ß7 is required for this process. METHODS: We used a T cell-mediated colitis model to study the role of α4ß7 in the innate immune compartment. We then performed competitive bone marrow (BM) reconstitution experiments to assess the requirement of α4ß7 in the generation of intestinal retinoic acid (RA)-producing CD11c(hi) DC (ALDE(+)DC) and CD64 macrophages. Using mixed BM chimeras we also asked whether α4ß7 is required to give rise to tolerogenic mononuclear phagocytes. RESULTS: Lack of ß7 integrins in the innate immune compartment (ß7(-/-)RAG2(-/-) mice) markedly accelerated T cell-mediated colitis, which was correlated with lower numbers and frequencies of ALDE(+)DC in mesenteric lymph nodes. Consistent with a role of α4ß7 in the generation of intestinal mononuclear phagocytes, BM cells from ß7(-/-) mice poorly reconstituted small intestine ALDE(+)DC and Mφ when compared to their wild type counterparts. In addition, mice lacking ß7 integrins in the CD11c(hi) compartment showed decreased ability to induce Foxp3(+) T(REG) and IL-10-producing T cells. CONCLUSIONS: Mice lacking ß7 integrins in the innate immune compartment are more susceptible to intestinal inflammation, which is correlated with a requirement of ß7 integrins to reconstitute gut mononuclear phagocytes with tolerogenic potential.

Altered microRNA profiles in bronchoalveolar lavage fluid exosomes in asthmatic patients.

BACKGROUND: Asthma is characterized by increased airway narrowing in response to nonspecific stimuli. The disorder is influenced by both environmental and genetic factors. Exosomes are nanosized vesicles of endosomal origin released from inflammatory and epithelial cells that have been implicated in asthma. In this study we characterized the microRNA (miRNA) content of exosomes in healthy control subjects and patients with mild intermittent asthma both at unprovoked baseline and in response to environmental challenge. OBJECTIVE: To investigate alterations in bronchoalveolar lavage fluid (BALF) exosomal miRNA profiles due to asthma, and following subway air exposure. METHODS: Exosomes were isolated from BALF from healthy control subjects (n = 10) and patients with mild intermittent asthma (n = 10) after subway and control exposures. Exosomal RNA was analyzed by using microarrays containing probes for 894 human miRNAs, and selected findings were validated with quantitative RT-PCR. Results were analyzed by using multivariate modeling. RESULTS: The presence of miRNAs was confirmed in exosomes from BALF of both asthmatic patients and healthy control subjects. Significant differences in BALF exosomal miRNA was detected for 24 miRNAs with a subset of 16 miRNAs, including members of the let-7 and miRNA-200 families, providing robust classification of patients with mild nonsymptomatic asthma from healthy subjects with 72% cross-validated predictive power (Q(2) = 0.72). In contrast, subway exposure did not cause any significant alterations in miRNA profiles. CONCLUSION: These studies demonstrate substantial differences in exosomal miRNA profiles between healthy subjects and patients with unprovoked, mild, stable asthma. These changes might be important in the inflammatory response leading to bronchial hyperresponsiveness and asthma.

Proinflammatory exosomes in bronchoalveolar lavage fluid of patients with sarcoidosis.

BACKGROUND: Sarcoidosis is a systemic disease of unknown aetiology characterised by granuloma formation and the presence of interferon γ (IFNγ)-producing T cells that cause inflammation and tissue damage in multiple organs, especially the lung. Exosomes are nano-sized immunomodulatory vesicles of endosomal origin released from a diverse range of cells and are also found in physiological fluids including bronchoalveolar lavage fluid (BALF) from healthy individuals. OBJECTIVE: To investigate whether exosomes are enriched in the lungs of patients with sarcoidosis compared with healthy individuals and whether they could contribute to pathogenesis. DESIGN: BALF exosomes from patients with sarcoidosis (n=36) and healthy controls (n=14) were compared by electron microscopy, flow cytometry, western blot analysis and mass spectrometry. BALF exosomes were incubated with autologous peripheral blood mononuclear cells (PBMCs) or the human bronchial epithelial cell line 16HBE14o-. Cytokines were measured by ELISPOT and ELISA. RESULTS: BALF from patients with sarcoidosis showed increased levels of exosomes compared with healthy individuals. Exosomes from patients showed significantly higher expression of MHC class I and II, tetraspanins CD9, CD63 and CD81 as well as neuregulin-1, known to be associated with cancer progression. Furthermore, BALF exosomes from patients induced significantly higher IFNγ and interleukin (IL)-13 production in autologous PBMCs compared with healthy individuals and could also stimulate IL-8 production from epithelial cells. CONCLUSION: The results indicate for the first time a role for exosomes in human lung disease with possible contributions to the initiation and progression of inflammation in sarcoidosis. This suggests that exosomes may be a new potential target for the clinical treatment of lung diseases.