Role of lymphocytes in the ovine response to endotoxin.

The involvement of thymocytes in the cardiopulmonary response to endotoxin was studied in chronically instrumented sheep. Four hours after the administration of 0.75 microgram/kg of endotoxin the blood levels of thymocytes were less than 25% of the control value, at a time when there was a marked fall in the cardiac index and a rise in pulmonary lymph flow. In a second series of experiments sheep were depleted of their thymocytes by the administration of antithymocyte serum. When endotoxin was given to these animals the cardiac output did not fall to the same extent, nor did the hematocrit rise as much as it did in the intact animal. It thus appears that the thymocyte may play a contributing role in the cardiopulmonary response to endotoxin.