PUB - Publikationen an der Universität Bielefeld

Scanning electron microscopy has been used to examine the changes in the basement membrane structure induced by polymorphonuclear leukocytes during leukodiapedesis. A diapedesis model based on a Boyden chamber fitted with a human amnion membrane simulated inflammatory processes during which leukocytes are stimulated to leave blood vessels and to penetrate basement membranes. In the Boyden chamber, a chemotactic gradient was developed from a solution of 10(-7) M formyl-methionyl-leucyl-phenylalanine, which induced the cells to migrate through the membrane. Our observations suggest that leukocytes, like tumor cells, emigrate in a three-step process. In the first instance, they adhere to the basement membrane. A local partial proteolysis follows, which is caused by secreted metalloproteinases, especially by gelatinase. The partial dissolution of the matrix facilitates cell penetration. Active locomotion and squeezing through the residual membrane matrix allows the cells to penetrate without complete local membrane destruction. The last step involves migration of the cells through the connective tissue barrier to the site of infection. The type I collagen fibres which form this loose stroma tissue are no obstacle and can be pushed aside without proteolytic degradation.