Changes in ¹³¹I-labelled immune bovine γ-globulin during transmission to the circulation after oral adminstration to the young rat

Bovine γ-globulin, trace-labelled with ¹³¹I, reaches the circulation in substantial amounts although bacterial agglutinins from bovine antisera appear to be completely excluded. Thus when the bovine globulin is both isotopically labelled and immune, the labelled protein which reaches the circulation is still precipitable by antisera to bovine globulin but is without antibody activity. When the labelled bovine γ-globulin that has reached the circulation from the gut of the young rat is fed a second time to another young rat it enters the circulation in relatively larger amounts. Such increase in the relative amounts absorbed is not produced by dilution of the original bovine globulin with young rat serum nor by intravenous screening of this globulin in young rats and must be attributed to the previous passage through the gut wall It is thus confirmatory evidence that such passage effects a change in the γ-globulin fed.