Cell composition and lymphocyte subsets in the bronchoalveolar lavage of normal pigs of different ages in comparison with germfree and pneumonic pigs.

For studies of lymphocyte kinetics in the different compartments of the lung, basic data on the cellular composition and lymphocyte subsets of porcine bronchoalveolar lavage (BAL) are essential. Therefore BAL was performed in pigs, and cytologic findings were studied using cytologic staining, enzyme cytochemistry, and immunologic labeling techniques. Four groups of normal pigs at different ages and of different breeds, 1 group with bacterial pneumonia, and 1 group of germfree animals were used. The total cell recovery was 10 x 10(6) in germfree pigs, in normal pigs it was 1.2-4 times higher, and in pneumonic pigs 23 times higher. The main cell type was macrophages, approximately 80% in normal and germfree and 50% in pneumonic pigs. The BAL contained 20% lymphocytes. Granulocytes were absent in normal BAL, but formed 30% of pneumonic BAL. Here the total number of macrophages was 3-9 times higher than normal, the total number of lymphocytes was 11-23 times higher. The proportion of surface immunoglobulin positive (sIg+) cells was 4.5% in the young and 8.5% in the older pigs, and of T cells it was 6% in the young and 14.9% in the older pigs. The BAL of germfree pigs contained few sIg+ cells and half of the normal number of T cells. In pneumonic animals the BAL contained twice the number of sIg+ and a normal percentage of T cells. The percentage of T-helper lymphocytes was approximately 2% without marked differences between the groups, whereas the percentage of T-suppressor lymphocytes varied significantly from 0.8% in germfree to 4% in young normal and 8% in the older pigs. In this respect the pneumonic pigs did not differ from the normal groups. The study shows that the pig is a suitable animal model for further investigation of the cellular immune system of the lung.