Dr. Kassai Tibor szerk.: Parasitologia Hungarica 2. (Budapest, 1969)

The gelatinolytic effect of equal volume mixtures of intestinal fluid and worm metabolic antigen is shown in Pig. 2. According to light transmission values for Pig. 2 the proteolytic activity of 1:50 and 1:100 dilutions of digestive fluid was completely inhibited by metabolic antigen. In the course of control tests by the biuret method it was found that 0.06 ml metabolic antigen (equivalent to 600 worms) was able to inhibit 1-2 U of Armour's trypsin. No difference was found between the amylase activity of intestinal fluid with and without antigen or buffer. Discussion Prom the investigations of SYMONS and PAIRBAIRN (1962) it is known that there is no decrease in the secretion of pancreatic trypsin and amylase in rats infected with N. brasiliensis

. Thus the metabolic products (antigen molecules) of worms present in the intestine unavoidably interact with proteolytic factors of intestinal fluid. There are essentially three possible consequences : 1. the metabolic antigens escape breakdown by virtue of enzyme inhibition; 2. the antigen molecules merely undergo changes indifferent from the point of view of antigenicity; 3. digestion unmasks new determinant groups of definite specificity in the antigen molecules. Our experiments show that in vitro the metabolic products of N. brasiliensis decrease the proteolytic activity of fluid obtained from the small intestine. The inhibition is slight if related to the entire amount of intestinal fluid but in vivo a