APPLICATION OF POLY(L-LACTIC ACID) PARTICLES FOR THE SUPPRESSION OF GENETIC-RESISTANCE TO BONE-MARROW ALLOGRAFTS BY RETICULOENDOTHELIAL SYSTEM-BLOCKADE

We have recently successfully acheived bone marrow allografts by retic uloendothelial system (RES)-blockade. Long-term survival of the recipi ent mice after BMT was achieved without apparent evidence of graft-ver us-host disease (GVHD), although T-cells were not depleted from donor marrow cells. Hemopoietic system of these recipient mice was replaced by that of donor origin [7]. As a first step to the application of thi s technique for human patients, we tested poly(L-lactic acid) (PLLA) p articles as biogradeable particles. PLLA particles were phagocytized b y macrophages when injected intravenously, and degraded slowly. PLLA h as already been in clinical use as a bioresorbable suture material and matrix for drug release. We found that administration of PLLA prior t o bone marrow transplantation resulted in a successful take of the all ografts. In addition, PLLA was found not to show any antigenicity in n ormal mice.