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. 