The role of the thoracic duct lymph in cancer dissemination

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LYMPHATIC ABSORPTION OF CHOLESTEROL IN THE DOG FOLLOWING CORN OIL AND BUTTERFAT FEEDING

Lymphatic absorption of cholesterol was determined in 11 unanaesthetized dogs with thoracic duct bypasses or fistulae, following the administration of corn oil or butterfat with and without cholesterol supplementation. Comparisons based on fixed amounts of lymph or total lymph lipid, as well as the estimated overall sterol recoveries, showed that the conclusions can vary depending on how the calculations are done. On the basis of data collected in the same animal, it was concluded that the glyceride type of dietary fat had no significant effect on lymphatic absorption of cholesterol in the dog. The feeding of butterfat, corn and coconut oils, or simple triglycerides to different animals resulted in widely varying lymph cholesterol levels, which could not be correlated with any of the variables under direct experimental control.

THE EFFECT OF INTRAPERITONEAL INJECTION OF THORACIC DUCT LYMPHOCYTES FROM NORMAL AND IMMUNIZED RATS IN MICE INOCULATED WITH THE LANDSCHUTZ ASCITES TUMOUR

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THE ROUTE OF RE-CIRCULATION OF LYMPHOCYTES IN THE RAT

The experiments presented in this paper support the idea that the output of small lymphocytes from the thoracic duct of the rat (about 10 9 /day) is normally maintained by a large-scale re-circulation of cells from the blood to the lymph. It has been shown that the main channel from blood to lymph lies with in the lymph nodes and that small lymphocytes enter the nodes by crossing the walls of a specialized set of blood vessels, the post-capillary venules. In order to trace the fate of small lymphocytes, cells from the thoracic duct of rats were incubated for 1 h in vitro with tritiated adenosine. This labelled the RNA of about 65% of the small lymphocytes and more than 95% of the large lymphocytes; it also labelled the DNA of a proportion of the large lymphocytes. The mixture of small and large labelled lymphocytes was transfused into the blood of two groups of rats which belonged to the same highly inbred strain as the cell donors. At various times after the transfusions the thoracic ducts in one group of rats were cannulated to determine the proportion of labelled cells which could be recovered in the lymph; at corresponding times, the rats in the other group were killed and autoradiographs prepared from their tissues to determine the location of the labelled cells. The radioactive label in the RNA of small lymphocytes was stable enough to ensure that the labelled small lymphocytes which were recovered in the lymph several days after a transfusion were those which had originally been transfused into the blood. When the thoracic duct was cannulated 20 to 27 h after a transfusion, about 70% of the labelled small lymphocytes which had been transfused into the blood could be recovered from the thoracic duct over a 5-day period of lymph collection. During the first 36 to 48 h after cannulation, while the total output of small lymphocytes was falling rapidly, the proportion of labelled cells in the lymph remained approximately constant. The pool of the animal’s own cells with which the labelled cells had mixed contained between 1·5 and 2 × 10 9 small lymphocytes; this was identified as the re-circulating pool. An autoradiographic study showed that after their transfusion into the blood the labelled small lymphocytes ‘homed’ rapidly and in large numbers into the lymph nodes, the white pulp of the spleen and the Peyer’s patches of the intestine. The concentration of labelled cells in other tissues was trivial in comparison. Labelled small lymphocytes were seen penetrating the endothelium of the post-capillary venules in the lymph nodes within 15 min of the start of a transfusion; they were traced into the cortex of the nodes and finally into the medullary lymph sinuses. Labelled small lymphocytes did not migrate into the adult thymus but a few entered the thymus of newborn rats. It was concluded that the re-circulating pool of small lymphocytes was located in the lymphoid tissue, the thymus excepted, and that the rapid ‘homing’ of cells into the lymph nodes had its basis in the special affinity of small lymphocytes for the endothelium of the post-capillary venules. The interpretation of these experiments was not complicated by the presence of large, as well as of small lymphocytes in the suspensions of labelled cells which were transfused. Other experiments, in which the large lymphocytes alone were labelled with tritiated thymidine, showed that most of them migrated from the blood into the wall of the gut where they assumed the appearance of primitive plasma cells; very few divided to form small lymphocytes.

THE ROLE OF LYMPHOCYTES IN THE SENSITIZATION OF RATS TO RENAL HOMOGRAFTS

In order to study the role of blood-borne small lymphocytes in the sensitization of rats to renal homografts 2 techniques for the perfusion of isolated rat kidneys were employed: (a) the in vitro perfusion of kidneys with thoracic duct cells suspended in either an artificial medium or in blood; the perfusates were then injected into rats syngeneic with the lymphocyte donors; (b) the in vivo perfusion of kidneys with blood issuing from the femoral artery and returning to the femoral vein of living rats. The degree of sensitization conferred on the recipients by the perfusates was assessed by applying a skin homograft from the kidney donor and scoring the epithelial necrosis at 6 days. The in vitro experiments indicated that parental strain thoracic duct cells, which had passed through an F₁ hybrid kidney could confer upon a parental rat sensitivity to an F₁ skin graft. Several perfusions with radioactively labelled lymphocytes showed that the injected cells migrated to the lymph nodes and spleen of the recipients Labelled large pyroninophilic cells were occasionally seen in the spleen and lymph nodes of recipients, and it was suggested that these had arisen from the injected cells. Although the in vitro perfusions with blood indicated that renal homografts might sensitize their hosts within 1 hour, the in vivo perfusions suggested that about 5 to 12 hours were required. The more rapid sensitization in vitro was possibly due to the more frequent opportunity for contact between lymphocytes and kidney vascular endothelium which was afforded by the conditions in vitro.

THE SURGERY OF INFANTILE OBSTRUCTIVE JAUNDICE

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