Post-capillary venules in the lymphatic tissues of mice bearing experimental neoplasia.

The lymph nodes, thymus and Peyer's patches of DBA/2 mice bearing an experimental tumor, mastocytoma, were assessed histologically with special reference to the structure of the post-capillary venules. For each of the lymphoid organ studied, the post-capillary venule score (PCV-S) was determined on the three grades (grades 1, 2 and 3) of the venules classified according to the height of the endothelial cells. The highest scores were obtained in the lymph nodes and Peyer's patches of the control animals. The scores in these lymphoid organs of the tumor-bearing mice were statistically highly significantly lower than in the control series. The lowest scores, however, were obtained in the nodes and patches of mice bearing mastocytoma after the previous treatment with anti-theta-globulin. The scores in the thymuses did not deviate from each other in the three series of mice studied. The findings of the present work support the concept that the structural state of the post-capillary venules in the lymph nodes and Peyer's patches is an important regulator of the T-lymphocyte recirculation in these organs. On the other hand, the venules of the thymus seem to be unrelated both structurally and functionally to the post-capillary venules of the nodes and Peyer's patches, and a new name of "junctional venules" has been proposed for these low endothelium walled venules of the thymus.