The metabolism of different immunoglobulin classes in irradiated mice. II. Role of the gut.

Adult CH mice were irradiated by 700 r or with the gut shielded. In similar experiments the gut alone was irradiated. The earlier observation of a selective and profound decrease of serum IgA, moderate decrease in IgG and IgG, and little change in IgM, was confirmed for the animals irradiated without protection of the gut. Similar effects were found when the gut alone was irradiated, whereas whole-body irradiation with the gut shielded caused only little change in the different serum immunoglobulins. Hence the characteristic responses of the serum immunoglobulins appeared to result from X-ray damage to the intestine. From this and a preceding study it was hypothesized that such damage resulted in moderate losses of IgG from the blood stream into the intestinal lumen, but that the selective and severe depression of serum IgA was mostly due to the escape, through the damaged epithelium, of that portion of the secretion from intestinal plasma cells which normally would have joined the blood stream.