CHARACTERIZATION OF IMMUNOCOMPETENT CELLS RECOVERED FROM RESPIRATORY-TRACT AND TRACHEOBRONCHIAL LYMPH-NODE OF NORMAL GUINEA-PIGS

Abstract

To gain insight into the structure of the lung''s immune system, the identity and function of immunocompetent cells in the broncho-alveolar air spaces and tracheobronchial lymph nodes of normal guinea pigs were examined. Guinea pig thymus-derived (T) lymphocytes (mediators of cellular immunity) were identified by their ability to form rosettes with rabbit erythrocytes (E rosettes). Bone marrow-derived (B) lymphocytes (mediators of humoral immunity) were identified by their ability to form rosettes with sheep erythrocytes sensitized with antibody and complement (EAC rosettes) and by the presence of surface immunoglobulin, detected by direct immunofluorescence. Total lung lavage yielded 14 .+-. 5.0 .times. 106 (mean .+-. SD) cells. There were 68 .+-. 5% cells of the monocyte-macrophage series as judged by morphology, the ingestion of latex particles and the uptake of neutral red; 20 .+-. 9% were eosinophils and 12 .+-. 5% were lymphocytes. Stable populations of T and B lymphocytes were recovered from guinea pig airways and tracheobronchial lymph nodes. T cells represented 76% of lymphocytes from the airways and 64% of lymphocytes in tracheobronchial lymph node; B cells equaled 14% and 30%, respectively. The functional potential of T cells present in the lung and tracheobronchial lymph node was demonstrated by their proliferative response to phytohemagglutinin. These results indicated that, although macrophages are the predominant cell type, viable T and B lymphocytes are present in the guinea pig broncho-alveolar air space. The composition of these cells is comparable to what was observed in normal human lungs and shows that the guinea pig may be a useful model for humans. A method is described which uses 2 vital stains whereby macrophages, lymphocytes and rosetted lymphocytes can be distinguished in unseparated cell suspensions prepared from bronchial aspirates.