Effects of exogenous oestradiol on the number and functional capacity of circulating mononuclear and polymorphonuclear leukocytes in the sow.

The effects of exogenous oestradiol-17 beta on blood leukocytes were studied in four ovariectomized gilts. The gilts were injected with oestradiol benzoate dissolved in arachidic oil during the test period and 6 weeks later, during the control period, with arachidic oil alone. During both periods, the immune status of the blood was monitored by determining the total numbers of leukocytes, lymphocytes and neutrophils and the percentage of immunoglobulin (Ig)-bearing mononuclear cells. The serum level of Ig, the number of circulating monocytes with phagocytic activity and the phagocytic function of circulating polymorphonuclear leukocytes, estimated by means of chemiluminescence, were also determined. During the test period, the total number of lymphocytes and the proportion of Ig-bearing mononuclear cells in blood decreased significantly (P less than 0.05 and P less than 0.01 respectively) after treatment with oestradiol benzoate. For the polymorphonuclear cells, the time needed to reach the peak value of chemiluminescence was significantly (P less than 0.01) prolonged after treatment; the phagocytic capacity of polymorphonuclear leukocytes was increased (P less than 0.01) concurrently. None of the changes recorded during the test period occurred during the control period. The results show that oestradiol-17 beta depresses some components of the vascular compartment of the porcine immune system, and stimulates other components.