REGULATION OF T-CELL FUNCTION IN LUNG-TISSUE BY PULMONARY ALVEOLAR MACROPHAGES

Collagenase digestion of perfused, lavaged rat lung yields a large pop ulation of CD5+ T cells, which on current evidence appear to be recent ly derived from the peripheral blood pool. Two-colour cytofluorographi c analysis indicates that approximately 65% are CD4+ T cells, which ar e predominantly of the activated/memory phenotype. By limiting dilutio n analysis, these peripheral lung wall T cells and their airway counte rparts isolated by bronchoalveolar lavage, exhibit markedly reduced ca pacity to proliferate by comparison to peripheral blood T cells. Howev er, intratracheal inoculation of liposomes containing dichloro-methyle ne-diphosphonate at a dosage shown to eliminate the majority of reside nt alveolar macrophages (AM) rapidly restores the immunocompetence of these lung T-cell populations. These results are discussed in relation to recent reports that in vivo elimination of AM from rats and mice g reatly amplifies immune responses to inhaled antigens, in particular T -memory cell-dependent secondary antibody responses.