Purification of adrenal chromaffin cells increases antinociceptive efficacy of xenotransplants without immunosuppression

We have found that immunosuppression is necessary for the survival of xenog eneic adrenal medullary transplants. Because chromaffin cells are essential ly nonimmunogenic, it is likely that the highly immunogenic "passenger" cel ls in the transplant preparation bring about rejection. This article descri bes a procedure that produces an essentially pure preparation of chromaffin cells for transplantation. Bovine adrenal medullary cells were isolated an d differentially plated, resulting in a semipurified preparation of chromaf fin cells. Ferromagnetic beads were added to the cell suspension, some of w hich were phagocytized by endothelial cells, which allowed their removal by exposure to a magnet. The remaining cells were then exposed to ferromagnet ic beads coated with isolectin Bq from Griffonia simplicifolia and once aga in to a magnetic field. The "semipurified" preparation contained approximat ely 90% chromaffin cells, whereas the "highly purified" preparation was > 9 9.5% chromaffin cells as determined immunohistochemically. The immunogenici ty of the two cell preparations was assessed in vitro by determining their capacity to evoke lymphocyte proliferation. Rat spleen lymphocytes were mix ed with either a highly purified or semipurified population of bovine chrom affin cells. The results of this assay demonstrated that the highly purifie d preparation was a much weaker stimulant of lymphocyte proliferation than was the semipurified preparation and may demonstrate better graft survival in vivo. Transplantation via intrathecal catheter of either 80,000 or 250,0 00 cells from the highly or partially purified preparations onto the lumbar spinal cord of nonimmunosuppressed and nonnicotine-stimulated rats produce d a cell number-dependent antinociception for both A delta and C fiber-medi ated thermonociception at 6 days after transplantation. After 6 days and up to 28 days, only the "highly purified" preparation showed antinociception. These results suggest that nearly complete purification of bovine chromaff in cells minimizes immunorejection of xenogeneic transplants of these cells .