Demonstration of human leukocyte degranulation induced by sera from homozygotes and heterozygotes for cystic fibrosis

Abstract

The ability of epsilon-amino caproic acid (EACA)-treated normal serum and of cystic fibrosis (CF)-affected and carrier sera to promote the release of lysosomal enzymes from sensitized human polymorphonuclear leukocytes (PMN) was assessed through the measurement of beta-glucuronidase and myeloperoxidase activity after exposure of these cells to the various test sera. This study was initiated to extend the analogies between preciliary dyskinesia factor (pre-CDF), separated from the cell-free media of cultures derived from CF homozygous and heterozygous individuals, and C3a anaphylatoxin. The extent of lysosomal degranulation of human PMN exposed to fresh untreated sera of each of five controls, seven CF homozygotes, and eight heterozygotes, as expressed by the amount of beta-glucuronidase releases, was 7.84% (+/- 0.934) for countrol sera, 14.01% (+/- 1.79) for CF-affected sera, and 10.61% (+/- 1.43) for heterozygous sera. The difference between CF homozygotes and control subjects is significatn (P less than 0.0001), as is the difference between CF-affected and carrier individuals (0.001 less than P less than 0.005) and between control subjects and carriers (0.001 less than P less than 0.005), when beta-glucuronidase. However, the differences between control subjects and CF heterozygous individuals are not significant. Treatment of these sera with 1 M EACA gave values for beta-glucuronidase and myeloperoxidase release which are slightly reduced when compared with those obtained with fresh, untreated samples. EACA apparently reduces the activity of beta-glucuronidase released from PMN. Amicon filtration studies of these serum samples demonstrated that degranulating ability and the presence of cilicary dyskinesia, as assessed by rabbit tracheal bioassay, are not always associated. Therefore, the relationship between pre-CDF and the degranulator activity in native CF-affected and carrier sera is unclear, in part because of the limitations inherent in the test systems employed.