Elevated myeloid: plasmacytoid dendritic cell ratio associates with early acute cellular rejection in pediatric small bowel transplantation.
ABSTRACT Acute cellular rejection affects more than 60% of children after small bowel transplantation (SBTx). Dendritic cells (DCs) are potent antigen-presenting cells, modulate immune responses to gut microbes, and may serve as markers of rejection-prone small bowel transplantation (SBTx).
Myeloid CD11c DC (MDC), which may have inflammatory functions, and plasmacytoid CD123 DC (PDC), which may have tolerogenic potential, were measured by flow cytometric analysis, longitudinally (pretransplant, and at days 1 to 60, 61 to 200 posttransplant) in 23 children after SBTx. All children received cadaveric allografts with rabbit anti-human thymocyte globulin induction and steroid-free tacrolimus maintenance therapy. Rejectors were those children (n=16), who experienced biopsy-proven acute cellular rejection within 60 days of SBTx.
Of 69 maximum possible observations, 62 were available for analysis. Among rejectors, a significantly higher MDC:PDC ratio (P=0.004) was associated with numerically higher MDC counts and significantly lower PDC frequencies (P=0.017) during the 1- to 60-day time period, compared with nonrejectors. Logistic regression analysis, leave-one-out cross-validation, and receiver operating characteristic analysis revealed that MDC:PDC ratio more than or equal to 1.52 was associated with rejector status with sensitivity/specificity of 86/67% during the 1- to 60-day risk period for early SBTx rejection. Repeated measures analysis showed a significantly higher MDC:PDC ratio (P=0.043, F-test) among rejectors, compared with nonrejectors in cumulative data for pre-SBTx and 1- to 60-day time points. No correlation was seen between DC subsets and tacrolimus blood concentration at any time point.
We conclude that an elevated MDC:PDC ratio associates with early small bowel allograft rejection and may, therefore, identify at-risk recipients in the clinic.
- SourceAvailable from: Mohamed B. Ezzelarab[show abstract] [hide abstract]
ABSTRACT: The pursuit of clinical transplant tolerance has led to enhanced understanding of mechanisms underlying immune regulation, including the characterization of immune regulatory cells, in particular antigen-presenting cells (APC) and regulatory T cells (Treg), that may play key roles in promoting operational tolerance. Dendritic cells (DC) are highly efficient APC that have been studied extensively in rodents and humans, and more recently in non-human primates. Owing to their ability to regulate both innate and adaptive immune responses, DC are considered to play crucial roles in directing the alloimmune response towards transplant tolerance or rejection. Mechanisms via which they can promote central and peripheral tolerance include clonal deletion, the induction of Treg, and inhibition of memory T cell responses. These properties have led to the use of tolerogenic DC as a therapeutic strategy to promote organ transplant tolerance. In rodents, infusion of donor- or recipient-derived tolerogenic DC can extensively prolong donor-specific allograft survival, in association with regulation of the host T cell response. In clinical transplantation, progress has been made in monitoring DC in relation to graft outcome, including studies in operational liver transplant tolerance. Although clinical trials involving immunotherapeutic DC for patients with cancer are ongoing, implementation of human DC therapy in clinical transplantation will require assessment of various critical issues. These include cell isolation and purification techniques, source, route and timing of administration, and combination immunosuppressive therapy. With ongoing non-human primate studies focused on DC therapy, these logistics can be investigated seeking the optimal approaches. The scientific rationale for implementation of tolerogenic DC therapy to promote clinical transplant tolerance is strong. Evaluation of technical and therapeutic logistic issues is an important next step prior to the application of tolerogenic DC in clinical organ transplantation.Seminars in Immunology 07/2011; 23(4):252-63. · 5.93 Impact Factor
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ABSTRACT: The activity of α-1,2-mannosidase I is required for the conversion of high-mannose to hybrid-type (ConA reactive) and complex-type N-glycans (Phaseolus vulgaris-leukoagglutinin [PHA-L] reactive) during posttranslational protein N-glycosylation. We recently demonstrated that α-1,2-mannosidase I mRNA decreases in graft-infiltrating CD11c(+) dendritic cells (DCs) prior to allograft rejection. Although highly expressed in immature DCs, little is known about its role in DC functions. In this study, analysis of surface complex-type N-glycan expression by lectin staining revealed the existence of PHA-L(low) and PHA-L(high) subpopulations in murine splenic conventional DCs, as well as in bone marrow-derived DC (BMDCs), whereas plasmacytoid DCs are nearly exclusively PHA-L(high). Interestingly, all PHA-L(high) DCs displayed a strongly reduced responsiveness to TNF-α-induced p38-MAPK activation compared with PHA-L(low) DCs, indicating differences in PHA-L-binding capacities between DCs with different inflammatory properties. However, p38 phosphorylation levels were increased in BMDCs overexpressing α-1,2-mannosidase I mRNA. Moreover, hybrid-type, but not complex-type, N-glycans are required for TNF-α-induced p38-MAPK activation and subsequent phenotypic maturation of BMDCs (MHC-II, CD86, CCR7 upregulation). α-1,2-mannosidase I inhibitor-treated DCs displayed diminished transendothelial migration in response to CCL19, homing to regional lymph nodes, and priming of IFN-γ-producing T cells in vivo. In contrast, the activity of α-1,2-mannosidase I is dispensable for LPS-induced signaling, as well as the DCs' general capability for phenotypic and functional maturation. Systemic application of an α-1,2-mannosidase I inhibitor was able to significantly prolong allograft survival in a murine high-responder corneal transplantation model, further highlighting the importance of N-glycan processing by α-1,2-mannosidase I for alloantigen presentation and T cell priming.The Journal of Immunology 03/2011; 186(9):5201-11. · 5.52 Impact Factor
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ABSTRACT: Recurrent rejection shortens graft survival after intestinal transplantation (ITx) in children, most of whom also experience early acute cellular rejection (rejectors). To elucidate mechanisms common to early and recurrent rejection, we used a test cohort of 20 recipients to test the hypothesis that candidate peripheral blood leukocyte genes that trigger rejection episodes would be evident late after ITx during quiescent periods in genome-wide gene expression analysis and would achieve quantitative real-time PCR replication pre-ITx (another quiescent period) and in the early post-ITx period during first rejection episodes. Eight genes were significantly up-regulated among rejectors in the late post-ITx and pre-ITx periods, compared with nonrejectors: TBX21, CCL5, GNLY, SLAMF7, TGFBR3, NKG7, SYNE1, and GK5. Only CCL5 was also up-regulated in the early post-ITx period. Among resting peripheral blood leukocyte subsets in randomly sampled nonrejectors, CD14(+) monocytes expressed the CCL5 protein maximally. Compared with nonrejectors, rejectors demonstrated higher counts of both circulating CCL5(+)CD14(+) monocytes and intragraft CD14(+) monocyte-derived macrophages in immunohistochemistry of postperfusion and early post-ITx biopsies from the test and an independent replication cohort. Donor-specific alloreactivity measured with CD154(+) T-cytotoxic memory cells correlated with the CCL5 gene and intragraft CD14(+) monocyte-derived macrophages at graft reperfusion and early post-ITx. CCL5 gene up-regulation and CD14(+) macrophages likely prime cellular ITx rejection. Infiltration of reperfused intestine allografts with CD14(+) macrophages may predict rejection events.American Journal Of Pathology 08/2011; 179(4):1929-38. · 4.52 Impact Factor