The migration test on circulating bovine leukocytes and its possible application in the diagnosis of Johne's disease

Abstract

The leukocyte migration test for in vitro studies of delayed type hypersensitivity has recently been reviewed (Søborg & Ben-dixen 1967; Bendixen & Søborg 1969). Søborg & Bendixen applied the test to circulating leukocytes in man and thereby widely increased the potentialities of this test. They obtained high leukocyte yields with only moderate erythrocyte admixture by harvesting the supernatant plasma after sedimentation of the erythrocytes for 60 min. at 37°C in the normal gravitational field (1 × g)- Their procedure was unsuitable for the present investigation because bovine erythrocytes sediment so slowly. Sedimentation after clumping at the interphase of aqueous solutions of polymers, dextran and methylcellulose, in combination with metrizoic acid (Böyum 1968) was tried without success because the vast majority of the leukocytes sedimented together with the erythrocytes. Separation of leukocytes from erythrocytes could not be achieved by differential centrifugation.