Effects of lymph diversion versus corticosteroids on blood and lymphocyte pools

Thoracic duct-rumen fistulae (TDRF) and low or high doses of Prednisolone were employed to induce depletion of blood and lymph node lymphocytes in calves. Elimination of the easily mobilizable pool of lymphocytes was almost complete within 6 days after commencing TDRF. Blood lymphocyte counts were reduced to approximately 1/3 of pre-TDRF levels. Prednisolone in low doses did not decrease the number of blood lymphocytes. High doses of Prednisolone induced a moderate, progressive blood lymphocytopenia. Both TDRF and low and high dose Prednisolone schedules induced a significant reduction of lymphocytes in lymph nodes. The loss of small lymphocytes from lymph nodes was almost entirely restricted to the diffuse cortical (paracortical) zone. The lymphocyte counts in the follicular cortex and in the medulla were not significantly affected. Almost complete disappearance of germinal centers was observed in lymph nodes of calves subjected to TDRF or high doses of Prednisolone.