Pulmonary immune cells in health and disease: lymphocytes.

Immunological defence mechanisms of the lung are provided by several different types of immunocompetent cell. Among these, the most important are lymphocytes, alveolar macrophages and neutrophils. This review focuses mainly on the pattern of physiological activities of pulmonary lymphocytes in the local host defences. The article provides an overview of the events leading to the recruitment, homing and activity of lymphocytes in the lower respiratory tract. The pathways through which the pulmonary lymphoid system recognizes, destroys and contributes to removing potentially harmful inhaled antigenic materials are also briefly discussed. The final section of the article highlights the pathogenetic role envisaged for lymphoid cells in disease states, in the context of the known biology of these cells.