Six-year clinical effect of donor bone marrow infusions in renal transplant patients

Background. To date, several single- and multicenter clinical trials have a ttempted to induce specific immunological unresponsiveness using donor bone marrow cell infusions to augment solid organ transplantation, but the outc omes have not been definitive. Methods. Between September 1994 and May 1998, 63 cadaver (CAD) renal transp lant recipients of either one or two postoperative donor bone marrow cell ( DBMC) infusions were prospectively compared with 219 non-infused controls g iven equivalent immunosuppression. There was at least a 1 HLA DR antigen ma tch present between donors and recipients. The immunosuppressive regimen in cluded a 10-day course of OKT3 induction, and tacrolimus, mycophenolate mof etil, and methylprednisolone maintenance. A total 7.01x10(8+/-)11.9x10(8) ( SD) DBMC/kg was infused into the CAD recipients on either days 4 and 11 (n= 42) or one half of that dose on day 4 (n=21) postoperatively, Clinical foll ow-up has ranged from 2.9 to 6.3 years (mean, 4.7 years). Studies were also performed of humoral immunity and quantitative cellular chimerism, Results, There is clear-cut equivalence in immunosuppressive dosaging and i n the other major demographic variables in both groups. However, only 2/63 DBMC recipients had biopsy-proven chronic rejection, whereas 41/219 showed chronic rejection in the controls (P=<0.01). In both groups, mortality was not associated with rejection, The actuarial graft survival at 6.3 years in the CAD DBMC group was 84.3% compared with 72.2% in the control group (not statistically significant). However, if death with a functioning graft was excluded, graft survival was 94.1% in the DBMC group and 79.8% in the cont rols (P=0.039). Forty patients in the control group continue to have deteri orating renal function (increasing serum creatinine concentrations to 2 mg/ dl and higher), compared with 2 patients in the DBMC group (P=0.04). In the DBMC group, chimerism in iliac crest marrow aspirates has increased 3-fold in yearly sequential measurements between 1 and 4 years postoperatively av eraging 1.3+/-0.36% (SE) most recently. This has not occurred in the contro ls. Conclusions. There now appears to be more solid long-term evidence, in kidn ey transplant recipients prospectively receiving DBMC infusions, of an impr ovement in long-term graft survival, and of the degree of chimerism positiv ely correlating with the absence of graft loss.