ABSTRACT
The immune inductive sites within these two compartments are the bronchus-associated lymphoid tissue (BALT) and draining nodes of the lungs that are situated around the hili and mediastinum. In humans, BALT exists during childhood as isolated lymphoid follicles in close contact with the surface epithelium. Just as the superficially and deeply located cervical lymph nodes receive lymphatic vessels from both nasopharynx-associated lymphoid tissue (NALT) and effector sites in the upper respiratory tree, the parabronchial, hilar, and paratracheal lymph nodes drain the airway mucosa distal to the pharynx, including the lung parenchyma. In addition to NALT and BALT, regional lymph nodes that drain the airways are also important inductive sites for the respiratory tract. The pathogenesis of asthma depends heavily on innate immune cells, including dendritic cells, alveolar macrophages, mast cells, basophils, eosinophils, natural killer T cells, and recently described innate lymphoid cells.
