Lysozyme activity in cystic fibrosis.

The activity of lysozyme in saliva and serum was determined in 51 patients with cystic fibrosis. Measurements were made on two occasions at least 1 month apart and compared to those of 25 normal healthy individuals of the same ages, sex, and race. The mean serum lysozyme activity of normal individuals was 5.8 micrograms/ml (S.E. = 0.4), whereas that of cystic fibrosis patients was 10.8 micrograms/ml (S.E. = 0.5). The difference is significant (P less than 0.05). Initial mean values compared to those of repeated samples from the cystic fibrosis group were similar, whereas individual fluctuations occurred between test periods. The mean lysozyme activity of the saliva sample of normal individuals was 63.5 micrograms/ml (S.E. = 9.3) and the mean value from cystic fibrosis patients was 82.7 (S.E. = 6.9). This difference was not significant (P greater than 0.1). Mean values from specimens obtained a month or longer after the initial saliva samples were similar for the two episodes. There was no correlation between the serum and salivary values and the age, sex or race of the subjects, the Shwachman-Kulczycki scores, colonization with Pseudomonas aeruginosa, Staphylococcus aureus or Haemophilus influenzae or absolute white blood cell counts. In vitro studies failed to demonstrate bactericidal activity for mucoid and nonmucoid strains of P. aeruginosa or for S. aureus. Elevated lysozyme activity in cystic fibrosis may be related to either an increased granulocyte turnover because of chronic bacterial infection of the respiratory tract or to a basic defect in the lysosomal membrane allowing an increased release of the enzyme, or a combination of both.