A method for bronchoalveolar lavage in live pigs

In order to isolate porcine alveolar macrophages and to quantitatively study the components of recovered lung fluid, a bronchoalveolar lavage technique in living pigs was developed. Lung lavage was performed after introducing a catheter through the mouth via the trachea in the diaphragmatical lobe. Thirty ml of phosphate-buffered saline (PBS) was introduced into the lung and the fluid was aspirated after one minute. Following this, another 15 ml of PBS was introduced into the lung and aspirated after one minute. The recovered volume of the second lavage averaged 15 ml (+/- 0.4 S.E.M.). Cells thus obtained from specific-pathogen-free (SPF) pigs were composed of 98% macrophages. Lavage fluids from conventionally bred pigs contained 67% macrophages, 17% neutrophilic granulocytes and about 16% lymphocytes, demonstrated by their morphology and acid phosphatase activity. The viability of the recovered cells was over 98% in both SPF and conventionally bred pigs. The dilution of the aspirated lung liquid was determined by using methylene blue in the introduced fluid. The calculated dilution factor of the recovered lavage fluid was 0.58 (S.E.M. 0.02). No influence was noticed on the number or composition of cells nor on the dilution factor when lung lavage was done in SPF pigs twice a week during a four week period. The protein concentration in lavage fluid from SPF pigs was 142 (SD +/- 26) mcg/ml. In conventionally bred pigs, however, a wide variation (276 +/- 229 mcg/ml) in protein content was noted. Lavage fluid supernatant of some animals had a bactericidal effect on Haemophilus pleuropneumoniae strain 13261, whereas no bactericidal effect was noted in other lavage samples.