Alloimmune responses driven by donor-specific antibodies (DSAs) can lead to antibody-mediated rejection (ABMR) in organ transplantation. Yet, the cellular states underlying alloreactive B cell responses and the molecular components controlling them remain unclear. Using high dimensional profiling of B cells in a cohort of 96 kidney transplant recipients, we identified expanded numbers of CD27+CD21- activated memory (AM) B cells that expressed the transcription factor T-bet in patients who developed DSAs and progressed to ABMR. Notably, AM cells were less frequent in DSA+ABMR- patients and at baseline levels in DSA- patients. RNA-seq analysis of AM cells in patients undergoing ABMR revealed these cells to be poised for plasma cell differentiation and to express restricted IGHV sequences reflective of clonal expansion. In addition to T-bet, AM cells manifested elevated expression of IRF4 and Blimp1, and upon co-culture with autologous T follicular helper cells, differentiated into DSA-producing plasma cells in an IL-21 dependent manner. The frequency of AM cells was correlated with the timing and severity of ABMR manifestations. Importantly, T-bet+ AM cells were detected within kidney allografts along with their restricted IGHV sequences. This study delineates a pivotal role for AM cells in promoting humoral responses and ABMR in organ transplantation and highlights them as important therapeutic targets.
Kevin Louis, Elodie Bailly, Camila Macedo, Louis Lau, Bala Ramaswami, Alexander Chang, Uma Chandran, Douglas Landsittel, Xinyan Gu, Geetha Chalasani, Adriana Zeevi, Parmjeet Randhawa, Harinder Singh, Carmen Lefaucheur, Diana Metes
Primary Graft Dysfunction (PGD) is the predominant cause of early graft loss following lung transplantation. We recently demonstrated that donor pulmonary intravascular non-classical monocytes (NCM) initiate neutrophil recruitment. Simultaneously, host-origin classical monocytes (CM) permeabilize the vascular endothelium to allow neutrophil extravasation necessary for PGD. Here, we show that a CCL2-CCR2 axis is necessary for CM recruitment. Surprisingly, although intravital imaging and multichannel flowcytometry revealed that depletion of donor NCM abrogated CM recruitment, single-cell RNA-seq identified donor alveolar macrophages (AM) as predominant CCL2 secretors. Unbiased transcriptomic analysis of murine tissues combined with murine knockouts and chimeras indicated that IL1β production by donor NCM was responsible for the early activation of AM and CCL2 release. IL1β production by NCM was NLRP3 inflammasome-dependent and inhibited by treatment with a clinically approved sulphonylurea. Production of CCL2 in the donor AM occurred through IL1R-dependent activation of the PKC and NFκB-pathway. Accordingly, we show that IL1β-dependent paracrine interaction between donor NCM and AM leads to recruitment of recipient CM necessary for PGD. Since depletion of donor NCM, IL1β or IL1R antagonism, and inflammasome inhibition, abrogated recruitment of CM as well as PGD, and are feasible using FDA-approved compounds, our findings may have potential for clinical translation.
Chitaru Kurihara, Emilia Lecuona, Qiang Wu, Wenbin Yang, Felix L. Nunez-Santana, Mahzad Akbarpour, Xianpeng Liu, Ziyou Ren, Wenjun Li, Melissa Querrey, Sowmya Ravi, Megan L. Anderson, Emily Cerier, Haiying Sun, Megan E. Kelly, Hiam Abdala-Valencia, Ali Shilatifard, Thalachallour Mohanakumar, G.R. Scott Budinger, Daniel Kreisel, Ankit Bharat
Altered inflammation and tissue remodeling are cardinal features of cardiovascular disease and cardiac transplant rejection. Neutrophils have increasingly been understood to play a critical role in acute rejection and early allograft failure; however, discrete mechanisms that drive this damage remain poorly understood. Herein, we demonstrate that early acute cardiac rejection increases allograft prolyl endopeptidase (PE) in association with de novo production of the neutrophil pro-inflammatory matrikine proline-glycine-proline (PGP). In a heterotopic murine heart transplant model, PGP production and PE activity were associated with early neutrophil allograft invasion and allograft failure. Pharmacologic inhibition of PE with Z-Pro-Prolinal reduced PGP, attenuated early neutrophil graft invasion, and reduced pro-inflammatory cytokine expression. Importantly, these changes helped preserve allograft rejection-free survival and function. Notably, within two independent patient cohorts, both PGP and PE activity were increased among patients with biopsy-proven rejection. The observed induction of PE and matrikine generation provides a novel link between neutrophilic inflammation and cardiovascular injury, represents a potentially new target to reduce allogenic immune responses, and uncovers a previously unrecognized mechanism of cardiovascular disease.
Gregory A. Payne, Nirmal S. Sharma, Charitharth V. Lal, Chunyan Song, Lingling Guo, Camilla Margaroli, Liliana Viera, Siva Kumar, Jindong Li, Melanie Bosley, Dongqi Xing, Xin Xu, J. Michael Wells, James F. George, Jose A. Tallaj, Massoud Leesar, J. Edwin Blalock, Amit Gaggar
Graft-versus-host disease (GVHD) is a pathological process caused by an exaggerated donor lymphocyte response to host antigens after allogeneic hematopoietic cell transplantation (allo-HCT). Donor T cells undergo extensive clonal expansion and differentiation, which culminate in damage to recipient target organs. Damage to the gastrointestinal tract is a main contributor to morbidity and mortality. The loss of diversity among intestinal bacteria caused by pretransplant conditioning regimens leads to an outgrowth of opportunistic pathogens and exacerbated GVHD after allo-HCT. Using murine models of allo-HCT, we found that an increase of Bacteroides in the intestinal microbiota of the recipients was associated with reduced GVHD in mice given fecal microbial transplantation. Administration of Bacteroides fragilis through oral gavage increased gut microbiota diversity and beneficial commensal bacteria and significantly ameliorated acute and chronic GVHD development. Preservation of gut integrity following B. fragilis exposure was likely attributed to increased short chain fatty acids, IL-22, and regulatory T cells, which in turn improved gut tight junction integrity and reduced inflammatory cytokine production of pathogenic T cells. The current study provides a proof of concept that a single strain of commensal bacteria can be a safe and effective means to protect gut integrity and ameliorate GVHD after allo-HCT.
M. Hanief Sofi, Yongxia Wu, Taylor Ticer, Steven Schutt, David Bastian, Hee-Jin Choi, Linlu Tian, Corey Mealer, Chen Liu, Caroline Westwater, Kent E. Armeson, Alexander V. Alekseyenko, Xue-Zhong Yu
The aryl-hydrocarbon receptor (AHR) is an intracellular sensor of aromatic hydrocarbons that sits at the top of various immunomodulatory pathways. Here, we present evidence that AHR plays a role in controlling IL-17 responses and the development of pulmonary fibrosis in response to respiratory pathogens following bone marrow transplant (BMT). Mice infected intranasally with gamma-herpesvirus 68 (γHV-68) following BMT displayed elevated levels of the AHR ligand, kynurenine (kyn), in comparison with control mice. Inhibition or genetic ablation of AHR signaling resulted in a significant decrease in IL-17 expression as well as a reduction in lung pathology. Lung CD103+ DCs expressed AHR following BMT, and treatment of induced CD103+ DCs with kyn resulted in altered cytokine production in response to γHV-68. Interestingly, mice deficient in the kyn-producing enzyme indolamine 2-3 dioxygenase showed no differences in cytokine responses to γHV-68 following BMT; however, isolated pulmonary fibroblasts infected with γHV-68 expressed the kyn-producing enzyme tryptophan dioxygenase (TDO2). Our data indicate that alterations in the production of AHR ligands in response to respiratory pathogens following BMT results in a pro-Th17 phenotype that drives lung pathology. We have further identified the TDO2/AHR axis as a potentially novel form of intercellular communication between fibroblasts and DCs that shapes immune responses to respiratory pathogens.
Stephen J. Gurczynski, Nicolas L. Pereira, Steven M. Hrycaj, Carol Wilke, Rachel L. Zemans, Bethany B. Moore
Understanding the distinct pathogenic mechanisms that culminate in allograft fibrosis and chronic graft failure is key in improving outcomes after solid organ transplantation. Here, we describe an F1 → parent orthotopic lung transplant model of restrictive allograft syndrome (RAS), a particularly fulminant form of chronic lung allograft dysfunction (CLAD), and identify a requisite pathogenic role for humoral immune responses in development of RAS. B6D2F1/J (H2-b/d) donor lungs transplanted into the parent C57BL/6J (H2-b) recipients demonstrated a spectrum of histopathologic changes, ranging from lymphocytic infiltration, fibrinous exudates, and endothelialitis to peribronchial and pleuroparenchymal fibrosis, similar to those noted in the human RAS lungs. Gene expression profiling revealed differential humoral immune cell activation as a key feature of the RAS murine model, with significant B cell and plasma cell infiltration noted in the RAS lung allografts. B6D2F1/J lung allografts transplanted into μMt–/– (mature B cell deficient) or activation-induced cytidine deaminase (AID)/secretory μ-chain (μs) double-KO (AID−/−μs−/−) C57BL/6J mice demonstrated significantly decreased allograft fibrosis, indicating a key role for antibody secretion by B cells in mediating RAS pathology. Our study suggests that skewing of immune responses determines the diverse allograft remodeling patterns and highlights the need to develop targeted therapies for specific CLAD phenotypes.
Keizo Misumi, David S. Wheeler, Yoshiro Aoki, Michael P. Combs, Russell R. Braeuer, Ryuji Higashikubo, Wenjun Li, Daniel Kreisel, Ragini Vittal, Jeffrey Myers, Amir Lagstein, Natalie M. Walker, Carol F. Farver, Vibha N. Lama
Myeloid cells are increasingly recognized as a major player in transplant rejection. Here, we used a murine kidney transplantation model and single-cell transcriptomics to dissect the contribution of myeloid cell subsets and their potential signaling pathways to kidney transplant rejection. Using a variety of bioinformatic techniques including machine learning, we demonstrated that kidney allograft-infiltrating myeloid cells followed a trajectory of differentiating from monocytes to pro-inflammatory macrophages, and exhibited distinct interactions with kidney allograft parenchymal cells. While this process correlated with a unique pattern of myeloid cell transcripts, a top gene identified was Axl, a member of the receptor tyrosine kinase family TAM (Tyro3/Axl/Mertk). Using kidney transplant recipients with Axl gene deficiency, we further demonstrated that Axl augmented intragraft differentiation of pro-inflammatory macrophages, likely via its effect on the transcription factor Cebpb. This in turn promoted intragraft recruitment, differentiation and proliferation of donor-specific T cells, and enhanced early allograft inflammation evidenced by histology. We conclude that myeloid cell Axl expression identified by single-cell transcriptomics of kidney allografts in our study plays a major role in promoting intragraft myeloid cell and T cell differentiation, and presents a novel therapeutic target for controlling kidney allograft rejection and improving kidney allograft survival.
Anil Dangi, Naveen R. Natesh, Irma Husain, Zhicheng Ji, Laura Barisoni, Jean Kwun, Xiling Shen, Edward B. Thorp, Xunrong Luo
In swine and nonhuman primates, kidney allografts can induce tolerance of heart allografts, leading to their long-term, immunosuppression-free survival. We refer to this phenomenon as kidney-induced cardiac allograft tolerance (KICAT). In this study, we have developed a murine model for KICAT to determine the underlining cellular/molecular mechanisms. Here, we show that spontaneously accepted DBA/2J kidneys in C57BL/6 recipients induce systemic tolerance that results in the long-term acceptance of DBA/2J heart allografts but not third-party cardiac allografts. The state of systemic tolerance of hearts was established 2 weeks after transplantation of the kidney, after which time, the kidney allograft is no longer required. Depletion of Foxp3+ T cells from these mice precipitated rejection of the heart allografts, indicating that KICAT is dependent on Treg function. Acceptance of kidney allografts and cotransplanted heart allografts did not require the thymus. In conclusion, these data show that kidney allografts induce systemic, donor-specific tolerance of cardiac allografts via Foxp3 cells, and that tolerance is independent of the thymus and continued presence of the kidney allograft. This experimental system should promote increased understanding of the tolerogenic mechanisms of the kidney.
Chao Yang, Jifu Ge, Ivy Rosales, Qing Yuan, Edward Szuter, Ellen Acheampong, Paul S. Russell, Joren C. Madsen, Robert B. Colvin, Alessandro Alessandrini
Acute rejection (AR) in renal transplantation is an established risk factor for reduced allograft survival. The incidence of AR is 10-20% despite standard of care immunosuppression, suggesting molecular pathways exist which are inadequately suppressed by current therapy. Molecules with regulatory control among these could serve as important targets for therapeutic manipulation to prevent rejection. Here, an integrative network-based computational strategy incorporating gene expression and genotype data of human renal allograft biopsy tissue was applied, to identify the master regulators- the key driver genes (KDGs)- within dyregulated AR pathways. A 982 meta-gene signature with differential expression in AR versus non-AR, was identified from a meta-analysis of microarray data from 735 human kidney allograft biopsy samples across seven data sets. Among the upregulated genes, enriched biologic processes include the immune response, leucocyte activation and antigen processing and presentation; where monocytes, macrophages and dendritic cells were identified as the major immune cell populations. Genomic key driver analysis of this signature predicted 14 KDGs. Expression of the KDGs provided risk stratification for subsequent graft loss with high prediction accuracy at 2 years post transplant (AUC=0.913) and 2 years post biopsy (AUC=0.889) in separate clinical cohorts. Interrogation of two drug-repositioning resources identified compounds with predicted efficacy against individual KDGs or a key driver-based gene set respectively, and therefore be repositioned for AR prevention. Minocycline, an FDA-approved tetracycline antibiotic, was chosen for experimental validation in a murine cardiac allograft model of AR. Minocycline alone attenuated the inflammatory profile of AR compared with controls, and when co-administered with immunosuppression prolonged graft survival. This study demonstrates the proof-of-concept that a network-based strategy, using gene expression and genotype data assists target prioritization for therapeutics in renal allograft rejection.
Zhengzi Yi, Karen L. Keung, Li Li, Min Hu, Bo Lu, Leigh Nicholson, Elvira Jimenez-Vera, Madhav C. Menon, Chengguo Wei, Stephen I. Alexander, Barbara Murphy, Philip J. O’Connell, Weijia Zhang
Acute graft versus host disease (aGvHD) remains a major impediment to successful allogeneic hematopoietic cell transplantation (allo-HCT). To solve this problem, a greater knowledge of factors which regulate the differentiation of donor T cells toward cytotoxic or regulatory cells is necessary. We report that the β2-adrenergic receptor (β2-AR) is critical for regulating this differentiation, and that its manipulation can control aGvHD without impairing the graft-versus-tumor (GvT) effect. Donor T cell β2-AR expression and signaling is associated with decreased aGvHD when compared to recipients of β2-AR–/– donor T cells. We determined that β2-AR activation skewed CD4+ T cell differentiation in vitro and in vivo toward regulatory T cells (Tregs) rather than the T helper 1 (Th1) phenotype. Treatment of allo-HCT recipients with a selective β2-agonist, (bambuterol) ameliorated aGvHD severity. This was associated with increased Tregs, decreased cytotoxic T cells, and increased donor bone marrow-derived myeloid derived suppressor cells (MDSCs) in allogeneic and humanized xenogeneic aGvHD models. β2-AR signaling resulted in increased Treg generation through glycogen synthase kinase-3 activation. Bambuterol preserved the GvT effect by inducing NKG2D+ effector cells and central memory T cells. These data reveal how β-AR signaling can be targeted to ameliorate GvHD severity while preserving GvT effect.
Hemn Mohammadpour, Joseph L. Sarow, Cameron R. MacDonald, George L. Chen, Jingxin Qiu, Umesh C. Sharma, Xuefang Cao, Megan M. Herr, Theresa E. Hahn, Bruce R. Blazar, Elizabeth A. Repasky, Philip L. McCarthy
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