Differences in exosome populations in human breast milk in relation to allergic sensitization and lifestyle.

BACKGROUND: Breast-feeding has many beneficial effects on the developing immune system of the newborn. Breast milk contains immunoregulatory factors, such as nano-sized vesicles named exosomes. This study aimed at characterizing breast milk exosomes from human early milk and mature milk and to investigate whether allergic sensitization and an anthroposophic lifestyle could influence the exosome profile. METHODS: Breast milk was collected from 22 mothers at day 3-8 and from 61 mothers at 2 months postpartum, all part of the ALADDIN birth cohort. Isolated exosomes were captured on anti-MHC-class II- or anti-CD63 beads and analyzed by flow cytometry. Exosomal phenotype was related to lifestyle and allergic sensitization of the mothers, and sensitization of the child at 2 years of age. RESULTS: We found a higher content of exosomes in early milk compared with mature milk. Early milk exosomes were enriched in HLA-DR molecules and displayed significantly lower levels of HLA-ABC compared with those in mature milk. Phenotypically different subpopulations of exosomes were found in mature milk. Significantly lower levels of MUC1 were detected on CD63-enriched exosomes from sensitized mothers compared with nonsensitized. Furthermore, women with an anthroposophic lifestyle had significantly lower MUC1 expression on their HLA-DR-enriched milk exosomes and up-regulated levels of CD63 on CD63-enriched exosomes compared with nonanthroposophic mothers. Notably, mothers whose children developed sensitization had an increased amount of HLA-ABC on their milk exosomes enriched for CD63. CONCLUSIONS: The phenotype of exosomes in breast milk varies with maternal sensitization and lifestyle, which might influence allergy development in the child.

Bronchoalveolar lavage fluid exosomes contribute to cytokine and leukotriene production in allergic asthma.

BACKGROUND: Leukotrienes (LTs) are potent pro-inflammatory mediators involved in asthma. Exosomes, nanosized vesicles released from various cells, can stimulate or down-regulate immune responses, depending on the state and nature of the originating cell. We have recently shown an altered exosome profile in bronchoalveolar lavage fluid (BALF) of patients with sarcoidosis, but their role in asthma is unknown. Our aims were to investigate whether exosomes from BALF have LT biosynthetic capacity and to explore phenotypic and functional characteristics of BALF exosomes in asthma. METHODS: Bronchoalveolar lavage fluid exosomes were collected from healthy individuals (n = 13) and patients with mild allergic asthma to birch pollen (n = 12) before and after birch allergen provocation. Exosomes were characterized by flow cytometry and Western blot. Their capacity to induce IL-8 and LT production in the human bronchial epithelial cell (BEC) line 16HB14o- was measured by ELISA and reverse-phase HPLC, respectively. RESULTS: Compared to BALF exosomes from healthy individuals, BALF exosomes from asthmatics displayed higher levels of exosome-associated markers, such as the tetraspanins CD63 and CD81 and the scavenger receptor CD36. No major differences were observed between BALF exosomes from before and after allergen provocation. Furthermore, we show that BALF exosomes contain enzymes for LT biosynthesis. The effect of exosomes to promote LTC(4) and IL-8 release in BEC was significantly increased for exosomes from asthmatics, and the CysLT(1) receptor antagonist Montelukast reduced exosome-induced IL-8 secretion. CONCLUSIONS: Bronchoalveolar lavage fluid exosomes from asthmatic and healthy individuals exhibit distinct phenotypes and functions. BALF exosomes from asthmatics might contribute to subclinical inflammation by increasing cytokine and LTC(4) generation in airway epithelium.