Patients with stable graft function in the DBMI group compared with control patients harbored microchimerism more frequently (94 vs. 3 donor genomes/million recipient genomes, p = 0.007), respectively, were higher in infused patients compared with controls. Thirty-one patients managed stable graft function; 17 in the DBMI group vs. 14 in controls. Patients with stable graft function in the DBMI group compared with control patients harbored microchimerism more frequently (94 vs. 50%, p = 0.01) and at higher concentrations (123 67 vs. Ketorolac 11 4, p = 0.007), respectively. Significant correlation between dose of infused cells and microchimerism levels was found post-transplant (p = 0.01). Using very sensitive assays, our findings demonstrate associations between the presence and quantity of microchimerism with stable graft function in infused patients. Keywords: donor bone marrow infusion, kidney allograft, microchimerism Introduction Allograft acceptance occurs when a two-way immune response results in reciprocal clonal exhaustion-deletion, which is usually understood to be the seminal mechanism for acquired tolerance after transplantation. Microchimerism, the persistence of a small quantity of donor cells in the host, may be a prerequisite for the maintenance of this situation (induced clonal deletion) and this form of tolerance has been shown to depend on a balance between microchimerism and anti-donor immunity.1-3 Based on the observation of prolonged systemic microchimerism in long-term allograft recipients, a number of trials were initiated to test the hypothesis that donor bone marrow cell infusion (DBMI) administered concurrently with transplant could augment tolerance.4-7 Miller et al.8 reported significantly decreased chronic rejection and higher graft survival rates in the presence of chimerism in kidney recipients with DBMI vs. non-infused recipients during six years follow up. Additionally, chimeric cells derived from iliac crest of infused kidney recipients had an inhibitory effect on anti-donor response in mixed lymphocyte reaction (MLR) suggesting the presence of regulatory Ketorolac elements.9 Similarly, in another study this inhibitory effect of chimeric cells in donor-specific MLR was shown for living related donor kidney recipients with DBMI vs. non-infused patients.10 Although elegant preclinical studies strongly suggest the importance of donor cell chimerism for active maintenance of T-cell unresponsiveness, the role of such cells in human studies remains unclear.11 In part, the inconsistent observations may be accounted for by the insensitive methodologyHLA-subtype specific flow cytometry to detect chimeric cells. With the advent of quantitative molecular techniques, microchimeric cells are detectable with up to 2 to 3 3 orders of magnitude greater sensitivity. Utilizing polymorphism-specific Rabbit Polyclonal to GPRIN2 quantitative PCR, we therefore set out to determine whether the persistence of microchimerism following low-dose DBMI without intensified conditioning would be associated with stable allograft Ketorolac function. Results Clinical outcomes Concurrent DBMI was well-tolerated and no graft vs. host disease was observed. Data given in Table 1 summarize the demographics and clinical characteristics with no statistically significant differences between Ketorolac both groups of patients except for cyclosporine A dosage at the end of the follow-up period. The number of HLA mismatches (A/B/DR) was nearly the same between both groups and all patients received an allograft with 2- 6 HLA mismatches. Table 1: Demographics and transplantation characteristics. nsns Open in a separate window **One case from each group was excluded from Mc analysis; in the DBMI group, because of uncontrolled bleeding treated with multiple blood transfusions; and in the control group, because of DNA contamination in post-transplant specimen. *Mean SE; ns, not significant. Open in a separate window Figure?1. Microchimerism levels (gEq/10^6 host cells) in different time intervals for patients with SGF from both groups. A significant difference was identified at days 7 and 30 post-operatively. *Mann-Whitney U test, 2-tailed p values. In the DBMI group, cell dose was correlated with microchimerism concentrations at day 7 (p = 0.01), day 14 (p = 0.03), and day 90 (p = 0.02) (Fig.?2ACC). Moreover, there was a significant inverse correlation between the microchimerism concentrations in the first week and serum creatinine levels at months 1, 6 and 12 (Fig.?2DCF), and also between microchimerism concentrations at month 1 and serum creatinine at days 14 and 30 post transplantation (Fig.?2GCH). Finally, an inverse correlation was found between dose of infused cells and serum creatinine levels at month 1 (r = -0.412, p = 0.07). Open in a separate window Figure?2. Bivariate correlation analysis for microchimerism levels, cell dose and serum creatinine levels among infused patients. A-C: Direct correlation between dose of infused cells (*10^8/recipients) and microchimerism concentrations (gEq/10^6 host cells) at day 7, 14 and 90. D-F: inverse correlation between microchimerism concentrations at day 7 and serum creatinine concentrations at month 1,.