Characterization of immunoreactive trypsin as a means of differentiating graft pancreatitis and allograft rejection after porcine pancreatic transplantation.

Graft pancreatitis and allograft rejection were both accompanied by increased serum levels of immunoreactive anionic trypsin (irAT) in a porcine pancreatic allograft transplantation model. Characterization of this immunoreactivity by gel filtration revealed different elution profiles in these conditions that can be helpful in the differentiation between them. During graft pancreatitis, a major part of the immunoreactivity was found within the high-molecular-weight fraction corresponding to the formation of complexes between trypsin and protease inhibitors. During allograft rejection, virtually all serum irAT increase could be attributed to the release of anionic trypsinogen without any evidence of activation. Since this transplantation model includes urinary diversion of the exocrine secretions, irAT and immunoreactive cationic trypsin (irCT) can also be measured in the urine. Characterization of this immunoreactivity showed that most of both irAT and irCT was found as active trypsin but a minor part was probably complexed with some protease inhibitor (possibly pancreatic secretory trypsin inhibitor [PSTI]).