Ultrastructure of the pulmonary lymphoid tissue.

Bronchial lymphoid tissue was studied by electron microscopy. Its structure is similar to that of a lymph node, with a zone 1 and zone 2, as previously described, and with postcapillary venules containing migrating lymphocytes in their walls, The lymphoid tissue is intimately related to the bronchial epithelium and lymphocytes, and in some places, monocytes and macrophages migrate between the epithelial cells.