[Antigenic properties of the proteolytic enzymes of the gastrointestinal tract].

Antigenic properties of crystalline pepsin, trypsin and chymotrypsin were studied in 9 rabbits immunised with these enzymes. Production of antibodies and their titres were investigated by means of the reaction of the precipitation in testing tubes and immunoelectrophoresis. The most clear antigenic properties were revealed in trypsin, and they were the weakest in pepsin. Low titres of the antibody to pepsin were, probably, due to denaturation of its molecule at physiological values of pH immunisation. Absence of cross-reactions of antisera to trypsin and chymotrypsin with pepsin solutions may be due to considerable structural differences of the antigenic determinants of pepsin from those of trypsin and chemotrypsin. However, antisera to trypsin and chemotrypsin do develop cross-reactions with respective enzymes and there were may be due to a similarity between structures of their antigenic determinants.