Characterization of immunocompetent cells recovered from the respiratory tract and tracheobronchial lymph node of normal guinea pigs.

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 X 10(6) (mean +/- SD) cells. There were 68+/-5 per cent cells of the monocyte-macrophage series as judged by morphology, the ingestion of latex particles, and the uptake of neutral red; 20+/-9 per cent were eosinophils, and 12+/-5 per cent were lymphocytes. Stable populations of T and B lymphocytes were recovered from guinea pig airways and tracheobronchial lymph nodes. T cells represented 76 per cent of lymphocytes from the airways and 64 per cent of lymphocytes in tracheobronchial lymph node; B cells equalled 14 per cent and 30 per cent, 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 has been observed in normal human lungs and provides preliminary evidence that the guinea pig may be a useful model for humans. This report also describes a method using 2 vital stains whereby macrophages, lymphocytes, and rosetted lymphocytes can be distinguished in unseparated cell suspensions prepared from bronchial aspirates.