Neuro-immune interaction in allergic airway inflammation: Expression and function of dendritic cells in sensory airway ganglia neurons
Introduction: Dendritic cells (DC) play as antigen-presenting cells a decisive role within the allergic inflammation. It has been shown that neuropeptides of sensory neurons like calcitonin gene-related peptide (CGRP) can attract and modulate immune cells like DC during the allergic airway inflammation. The colocalisation of DC and sensory airway nerves is, according to previous investigations, the crucial basis for neuroimmunological interaction in lung tissue. The aim of the present study is to evaluate possible extrapulmonary interactions of DC and neurons in ganglia during an allergic airway inflammation. Experimental methods: The sample material was received from a mouse model of chronic allergic airway inflammation. The BALB/c mice were treated with intranasal house dust mite (HDM) extract (25 µg/50 µl) for 5 days a week within a total period of 7 weeks. The jugularnodose ganglion complex was removed 24 hours after final allergen challenge and histological slices were prepared. Immunohistochemical staining was performed to detect the colocalisation of DC by MHC-II and CD11c and neurons by neuronal marker PGP 9.5. Result: We were able to prove for the first time that under physiological conditions dendritic cells are found in the vagal sensory airway ganglia of the mouse and that they increase significantly during an allergic airway inflammation (DCs/neurons: control 23.48 ± 7.613 % vs. HDM 49.75 ± 4.194 %, p = 0.0003). Additionally, an increased number of CGRP positive neurons in vagal sensory airway ganglia during allergic airway inflammation was found (CGRP positive neurons / total neurons: HDM 52.07 ± 3.040% vs. control 21.63 ± 3.799 %, p =0.0001). Discussion: The finding of the presence of DC in the airway jugular-nodose ganglion indicates a role of the DC in these ganglia under physiological conditions. The increased numbers of DC and CGRP-positive neurons in these ganglia suggest the involvement of these cells the pathogenesis of allergic airway inflammation. However, the exact functions of DC and CGRP in allergic airway inflammation remain to be explored in future studies.