Reutilization of DNA Breakdown Products from Lymphocytes in Lumen of Intestine

Migration of a very large number of lymphocytes (211.8 x 10⁶ per day) into the intestinal canal of rats, which weighed about 100 Gm., was found. Lymphocytes in the lumen of the intestine were 80.2 per cent small, 15.9 per cent medium and 3.9 per cent large. Any recycling of instilling cells into the intestine could not be observed. Lymphocytes labeled with H³-thymidine, obtained from both thymus and mesenteric lymph nodes of donor rats, were washed and injected into the intestine of recipient rats. H³ activity of the blood and thoracic duct lymph plasma after administration of labeled lymphocytes showed that DNA breakdown products from the lymphocytes in the gut were absorbed and transferred by way of both the portal vein and the thoracic duct. Evidence that the activity was actually incorporated into the DNA of proliferating cells of the recipient was demonstrated by autoradiographic means.