The metabolism of different immunoglobulin classes in irradiated mice: V. Contribution of the gut to serum IgA levels in normal and irradiated mice

It was demonstrated in earlier publications that the acute and selective fall in serum IgA levels in irradiated mice was due to a specific failure to renew the plasma pool of this immunoglobulin. In the present work, it is shown that irradiation causes some reduction in the rate of biosynthesis of IgA, but that this phenomenon only partly accounts for the observed disturbance in the metabolism of IgA. This conclusion is based both on direct measurements on the rate of biosynthesis in vitro of IgA by the isolated small bowel wall of irradiated and normal C(3)H mice, and on immunohistological studies and plasma cell counts on the gut, spleen and lymph nodes of these animals. On the other hand, it is shown that irradiated mice continue to excrete approximately normal amounts of IgA into their intestinal contents. The conclusion is that irradiation of the gut causes a rechannelling in the output of IgA synthesized by the plasma cells of the lamina propria, the major part being diverted to the intestinal lumen instead of being fed into the circulating pool of serum IgA