• Amani El-Gammal, John-Paul Oliveria, Karen Howie, Richard Watson, Patrick Mitchell, Ruchong Chen, Adrian Baatjes, Steven Smith, Dhuha Al-Sajee, Thomas J Hawke, Kieran J Killian, Gail M Gauvreau, and Paul M O'Byrne.
• 1 Firestone Institute of Respiratory Health.
• Am. J. Respir. Crit. Care Med. 2016 Jul 15; 194 (2): 169177169-77.

RationaleDendritic cells (DCs) are antigen-presenting cells essential for the initiation of T-cell responses. Allergen inhalation increases the number of airway DCs and the release of epithelial-derived cytokines, such as IL-33 and thymic stromal lymphopoietin (TSLP), that activate DCs.ObjectivesTo examine the effects of inhaled allergen on bone marrow production of DCs and their trafficking into the airways in subjects with allergic asthma, and to examine IL-33 and TSPL receptor expression on DCs.MethodsBone marrow, peripheral blood, bronchoalveolar lavage (BAL), and bronchial biopsies were obtained before and after inhalation of diluent and allergen from subjects with asthma that develop allergen-induced dual responses. Classical DCs (cDCs) were cultured from bone marrow CD34(+) cells. cDC1s, cDC2s, and plasmacytoid DCs were measured in bone marrow aspirates, peripheral blood, and BAL by flow cytometry, and cDCs were quantified in bronchial biopsies by immunofluorescence staining.Measurements And Main ResultsInhaled allergen increased the number of cDCs grown from bone marrow progenitors, and cDCs and plasmacytoid DCs in bone marrow aspirates 24 hours after allergen. Allergen also increased the expression of the TSLP receptor, but not the IL-33 receptor, on bone marrow DCs. Finally, inhaled allergen increased the percentage of cDC1s and cDC2s in BAL but only cDC2s in bronchial tissues.ConclusionsInhaled allergen increases DCs in bone marrow and trafficking of DCs into the airway, which is associated with the development airway inflammation in subjects with allergic asthma. Inhaled allergen challenge also increases expression of TSLP, but not IL-33, receptors on bone marrow DCs.

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