The Pulmonary-Alveolar Macrophage

(Second of Two Parts)Immunologic Functions of the Pulmonary-Alveolar Macrophage (PAM)The PAM functions importantly in pulmonary defense by participating in specific immunologic reactions and by interacting with other components of the immune system. The composition of the bronchoalveolar lymphoid system has been studied by means of bronchopulmonary lavage. These washings contain lymphocytes with T and B-surface markers as well as lymphocytes with "null" characteristics.111 112 113 114 In one study of human subjects, T cells comprised 47 per cent of the bronchial lymphocyte population, B cells 19 per cent and null cells 34 per cent.111 Human bronchopulmonary-lavage fluid contains IgA (both 11S . . .