FLOW-CYTOMETRIC ANALYSIS OF LEUKOCYTE ACTIVATION-INDUCED BY POLYETHYLENE-TEREPHTHALATE WITH AND WITHOUT PYROLYTIC CARBON COATING

Leukocyte activation is one test for the evaluation of blood-materials interaction. The expression of adhesion molecules analyzed by flow cy tometry provides a simple method to evaluate leukocyte activation by b iomaterials: any change in these molecules can be predictive of the in flammatory activity of the materials. In this study the contact betwee n leukocytes and uncoated polyethylene terephthalate or pyrolytic carb on-coated polyethylene terephthalate (PET and PET-PC, respectively) wa s inspected by analyzing whether the expression of some adhesion molec ules involved in leukocyte activation, namely LFA-1 (CD11a/CD18), Mac 1/CR3 (CD11b/CD18), and LECAM-1 (CD62L) can be modified. By flow cytom etry expression of the adhesion molecules can be studied separately on lymphocytes and myeloid cells. The materials tested reduced the total numbers of both leukocytes and neutrophils, although not significantl y. Neither PET nor PET-PC changed the expression of the adhesion molec ules in lymphocytes: this suggests that no specific immune response is stimulated. On the contrary, statistically significant changes were o bserved for monocytes and granulocytes: the percentage of cells expres sing Mac-1 and the density of such antigens on cell membranes increase d while the percentage of LECAM-1 positive cells decreased. Similar ch anges were observed when the cells underwent the inflammatory stimulus provided by an in vitro challenge with bacterial endotoxin. Our resul ts demonstrated that polyethylene terephthalate activates leukocytes b y modifying the expression in neutrophils of the molecules involved in the early phase of the inflammatory response. Even after coating PET with pyrolytic carbon, the ability of this material to activate circul ating leukocytes was maintained. (C) 1998 John Wiley & Sons, Inc.