The effect of long-term lymphatic drainage on the lympho-myeloid system in the guinea-pig.

Methods are described for the long-term drainage (9 or 10 days) of the mesenteric lymph duct in the guinea-pig and for the analysis of bimodal nuclear distributions by electronic sizing of lymphocytes in lymph. The present studies show that on the basis of nuclear volume, lymphocytes in mesenteric lymph consist of two populations (large and small) which are log-normally distributed. The relative proportions of the large and small lymphocytes and means and standard deviations of these component populations were estimated daily during the course of cannulation. The daily output of small lymphocytes was greatly reduced during the course of drainage to a base level of 110× 10 on day 6 which was maintained thereafter. The daily output of large lymphocytes was relatively constant at about 50× 10 throughout drainage. This finding is consistent with the view that many small lymphocytes are recirculating. The output of cells in mesenteric duct lymph on the 1st day of cannulation (379× 10) is similar to that recorded by other workers in thoracic duct lymph for the same period. Comparison of the present findings with the results of other studies shows that the level of indirect entry' lymphocytes and lymphocyte blood concentration remain remarkably constant while blood volume may be doubled. It is suggested that direct entry' of lymphocytes from lymphoid tissue to blood increases with age (body weight and, therefore, blood volume) of the animal. During lymphocyte depletion the concentration of bone marrow lymphocytes was reduced from 466,500 to 173,500/mm. There was no significant reduction in myeloid or erythroid cells. This finding suggests that either bone marrow lymphocytes are not involved in the production of erythroid and myeloid cells or that haemopoietic precursors are drawn from marrow lymphocytes produced rather than from those which are haematogenous in origin. Histological study of the lymphoid tissues of animals following long-term drainage showed a gross depletion of small lymphocytes in the cortex of nodes (particularly the mesenteric), white pulp of spleen and internodular areas of Peyers patches. The occurrence of large pyroninophilic cells with vesicular nuclei and prominent pyroninophilic nucleoli in depleted areas was noted. Mitotic figures were frequently observed in these cells. The thymus was not obviously affected by drainage.