Immune “tolerance profiles” in donor bone marrow infused kidney transplant patients using multiple ex vivo functional assays

Ex vivo identification of donor-specific unresponsiveness in organ transplant recipients is important for immunosuppression (IS) minimization. We tested three groups of stable living, related-donor kidney transplant patients up to 11 years postoperatively, i.e., 20 haploidenticals with donor bone marrow cell (DBMC) infusions, eight noninfused haploidentical controls (haplo controls), and 11 HLA-identical controls (HLA-id), using multiple ex vivo immune assays. We observed that no patients developed donor-specific antibodies. The majority showed donor-specific CTL unresponsiveness from year 1 onward. Thirteen of 20 DBMC recipients became specifically donor MLR nonreactive. Depletion of donor cells in DBMC recipients still MLR reactive increased donor-specific reactivity by 75% ± 36% (p = 0.04). Adding them back in low concentration caused antigen specific inhibition. The frequencies of ELISPOT granzyme-B and interferon-γ–producing cells somewhat paralleled the CTL and MLR responses. In the trans vivo DTH, 14 of 19 DBMC recipients demonstrated donor-specific unresponsiveness and 16 of 19 showed “linked suppression,” vs none of eight and one of eight haplo controls and vs six of 10 and one of 10 HLA-ids, respectively. Most importantly, when all six assays were performed simultaneously, 10 of 18 DBMC, five of 10 HLA-ids, and no haplo controls were specifically donor unresponsive long term. We propose that a cluster analysis combining these assays will reveal tolerant recipients in whom IS minimization may safely be tested. This appears to have occurred in many DBMC-infused recipients.