LACK OF IMMUNE-RESPONSES TO IMMEDIATE OR DELAYED IMPLANTED ALLOGENEICAND XENOGENEIC SCHWANN-CELL SUSPENSIONS

Previous studies have shown that Schwann cell implantation offers a po tential therapeutic approach to a variety of neurodegenerative disorde rs and traumatic injuries. In a clinically relevant paradigm, however, the implantation of autologous Schwann cells is problematic and the u se of heterogenetic Schwann cells will be required. In the present stu dy we addressed this important issue and analysed the immunogenicity a nd survival of allogeneic and xenogeneic Schwann cell suspension graft s in a prelesioned CNS fiber tract, the transected postcommissural for nix of the adult Wistar rat. Cultured Schwann cells from Wistar rat or human peripheral nerve were injected either immediately or after a de lay into the transection site and the spatio-temporal pattern of leuko cyte infiltration and of major histocompatibility antigen expression w as characterized and semiquantified with immunocytochemical methods. O ur main findings are that (1) invasive cerebral lesions induce the exp ression of MHC class I and II antigens, but only sparse infiltration o f T-lymphocytes, (2) both allogeneic and xenogeneic discordant Schwann cell suspension grafts, from either neonatal or adult peripheral nerv e, survive without any overt signs of rejection for up to 10 weeks aft er implantation; and (3) delayed implantation procedures have no effec t on immune responses to allogeneic Schwann cell grafts. These results demonstrate that there is no marked ongoing immune reactions to heter ogenetic Schwann cell suspension grafts and that long-term survival of cross-species Schwann cell grafts can be achieved in the absence of a ny immunsuppressive treatment. Thus the conditions for functional tran splantation of Schwann cells across immunological barriers seem to be favourable and will have implications for future cross-species studies , and possibly also for clinical application. (C) 1997 Wiley-Liss, Inc .