The migration of bronchoalveolar macrophages into hilar lymph nodes

The migration of bronchoalveolar macrophages (BAMs) into hilar lymph nodes (HLNs) was investigated in order to assess their potential importance in pulmonary immune responses. ⁵¹Chromium- or ¹¹¹Indium-labeled bronchoalveolar cells (BACs) or purified BAMs were inoculated into the tracheas of syngeneic guinea pigs, and the number of cells that reached HLN at 24-72 hours was estimated by 1) measuring the cell-associated radioactivity in HLN and 2) counting the radiolabeled cells in autoradiographic preparations. It was determined that 400-2900 BAM/10⁷ inoculated BACs or BAMs reached the HLNs within a 3-day period. From this data, it was calculated that in a normal animal as many as 8700 BAMs might reach HLNs daily. These migratory phagocytes are potentially important in facilitating the systemic spread of macrophage-resistant intracellular organisms from the lung. Furthermore, following phagocytosis and killing of microorganisms in the alveolus, BAMs might migrate to HLNs and present antigen to stimulate a primary immune response.