ADHESION AND PENETRATION OF HUMAN-LYMPHOC YTES THROUGH ALLOGENEIC ENDOTHELIAL-CELLS IN THE COURSE OF ORGAN REJECTION

Introduction: Cellular rejection mechanisms are characterized by the i nfiltration of sensitized lymphocytes through the donor endothelium in to the transplanted organ. The regulation of cellular adhesion molecul es by soluble mediators (cytokines) is thought to play a dominant role in this process. In the present study the kinetics of lymphocyte infi ltration were examined using a new established in vitro model and comp ared to the kinetics of adhesion molecule expression. Materials and Me thods: Peripheral blood lymphocytes (PBL) of healthy volunteers were p ipetted to allogeneic endothelial cell (EC) monolayers and binding rat es evaluated after different incubation times. Adherent PBL could be d istinguished from penetrated PBL by means of a combined phase contrast -/reflection interference contrast microscope. Results: 30-35% of all pipetted PBL adhered to unstimulated EC maximally. Out of these cells < 10% penetrated through the endothelium (= maximum penetration). The cytokines alpha-, beta-, gamma-interferon (IFN) or IL-1 did not enhanc e maximum adhesion, but accelerated this process. However, a 2 hrs pre stimulus of EC by these cytokines was necessary to induce acceleration . Maximum penetration was enhanced by alpha-, beta-, gamma-IFN, but no t by IL-1, irrespective whether PBL were added together with cytokines to unstimulated EC or to already prestimulated EC. Immunocytochemical and fluorometric analyses of adhesion molecule expression revealed a cytokine induced upregulation or de novo expression of the adhesion an tigens ICAM-1, ELAM-1 and VCAM-1 on EC membranes. Interestingly, PBL a dhered to EC before upregulation or de novo expression of adhesion mol ecules was detected. Discussion: The results showed that PBL adhesion and penetration processes were regulated differentially by cytokines. The early phase of PBL attachment to EC seemed not to be influenced by adhesion antigens but by an activation of tile lymphocyte cytoskeleto n.