Binding of 125I-labeled proteinases to plasma proteins in cystic fibrosis

Samples of plasma or serum from 53 cystic fibrosis (CF) patients, 90 relatives of CF patients , and 159 controls have been incubated with porcine or bovine 125I-trypsin, electrophoresed on polyacrylamide gel, and autoradiographed. In these individuals, the main binding protein for 125I-trypsin has been shown to be alpha 2-macroglobulin (alpha 2M). Using this method of analysis, no difference in electrophoretic migration of 125I-trypsin-alpha 2M complexes has been observed between CF and control individuals. However, trypsin binding to IgG has been observed in 80% of CF patients, 30% of their mothers, 3% of controls, and in two patients affected with pancreatitis. These trypsin binding immunoglobulins are called TbIg, and specifically, Tb1gG when referring to the G class. Experimental evidence indicates that binding of trypsin to IgG occurs through the Fab portion of the molecule. Tb1gG must be antibodies most probably induced by the exogenous trypsin ingested daily by most CF patients (and by patients affected with chronic pancreatitis). Antibodies against porcine pancreatic elastase have been observed using the same analysis, but not as frequently as Tb1g.