Immobilized heparin inhibits the increase in leukocyte surface expression of adhesion molecules

The effect of heparin coating of artificial materials on the surface expression of leukocyte surface molecules was assessed in blood from 9 donors in an experimental model of extracorporeal circulation. The leukocyte surface molecules CD11b, complement receptor type 3 (CR3), and CD45, leukocyte common antigen (LCA), on granulocytes and monocytes exposed to unmodified polyvinyl chloride tubes increased significantly compared with unmanipulated controls (p < 0.001) whereas a very modest and nonsignificant increase was observed in blood circulated in heparin-coated tubes. Accordingly, a highly significant reduction in expression of the 2 molecules was achieved by heparin coating (p < 0.001). The expression of CD11b and CD45 correlated with the degree of complement activation in plasma (rho = 0.6, p = 0.003). The expression of CD14 (endotoxin receptor) and CD16 (Fc gamma III receptor) was increased to the same extent in blood from unmodified and heparin-coated tubes (p < 0.02), and no correlation to complement activation was seen (rho = -0.275, p = 0.17 and rho = -0.004, p = 1, respectively). In conclusion, heparin coating of artificial surfaces has a substantial effect, reducing the expression of molecules involved in cellular adhesion and activation (CD11b and CD45), and the increase of these molecules by unmodified surfaces is complement dependent. In contrast, up-regulation of other surface molecules (CD14 and CD16) seems to be independent of heparin coating and complement activation and, thus, might be regulated by other mechanisms.