CLINICAL AND IN VITRO SUPPORT FOR IMMUNOREGULATION BY DONOR SPECIFIC BONE MARROW INFUSIONS IN RENAL TRANSPLANTATION

Abstract

11 Are there clinical effects of augmenting kidney transplantation with putatively immunoregulatory donor specific bone marrow cell (DBMC) infusions? Recipients of DBMC and kidney transplants from 63 cadaveric (CAD) and 30 living related (LR) donors have been studied beginning September, 1994, and November, 1996 respectively, through December 31, 1998. Recipients of 220 CAD kidneys, without bone marrow, treated with similar immunosuppression (OKT3 induction, Tacrolimus, Mycophenolate and Methylprednisolone) were considered controls. The actuarial 4 year clinical results, to date, demonstrate patient and graft survival in the DBMC CAD group of 93% and 92% respectively, versus that of the controls of 95% and 91%. Although there were still no essential differences in these parameters between the 2 groups, the effects of DBMC on chronic rejection (CR) with additional follow-up is now even more prominent than previously reported, i.e. 3 of 63 (5%) versus 35 of 220 (16%) (p=<0.01), in which, as of 12/31/97, one graft has now been lost in surviving patients in the DBMC group, in contrast to the controls in which 11 were lost. If only the 42 patients receiving 2 DBMC infusions were considered (as opposed to 21 who received one infusion due to insufficient numbers of DBMC) there were no graft losses. (p=<0.01). Quantitative donor cell chimerism has now increased three-fold in the iliac crest marrow of the DBMC infused CAD recipients using PCR-Flow analysis, i.e. 0.30%±0.07 at 1 year versus 1.30%±0.27 at 3 years in serial yearly studies on 19 patients. (p=<0.0001) The 2 year actuarial patient and graft survival in the LR DBMC group is 100%, (and no CR). Moreover, PCR-Flow assays of donor cell chimerism in recipient iliac crest bone marrow and peripheral blood detected even higher numbers of donor cells (>2 fold) than in the CAD group 1 year post-operatively (p=<0.001). This group, by contrast, received 25% of the total number of CAD marrow cells infused. A powerful proof of immunoregulatory reactions operative in LRD DBMC recipients was seen when after 1 year non-chimeric donor iliac crest marrow aspirates were simultaneously compared with chimeric recipient samples, both samples equivalently treated by isolation of donor Class I expressing cells using specific alloreactive monoclonal antibodies and immunomagnetic beads. (n=5) Donor specific MLC and CML reactions were inhibited using responding recipient PBL and serial dilutions of the isolated chimeric versus non-chimeric donor bone marrow cells as third party regulatory cells. There were ten-fold fewer of the chimeric donor cells (than non-chimeric donor cells) needed to regulate (inhibit by >50%) such reactions in vitro. We conclude that 4 years into this project, there is now substantial support for the immunoregulatory role of DBMC infusions in kidney transplant recipients in facilitating graft survival.