• T cell
• infection
• malignancy
• organ transplantation
• posttransplant complications
• rejection

• Basic and Applied Basic Research Foundation of Guangdong Province
• National Natural Science Foundation of China

• B lymphocytes
• T follicular helper cells
• chronic rejection
• donor specific antibody (DSA)
• immune regulation
• indirect alloresponse

• Humans
• Graft Rejection/immunology
• Isoantibodies/immunology
• B-Lymphocytes/immunology
• CD4-Positive T-Lymphocytes/immunology
• Germinal Center/immunology
• Chronic Disease
• Tissue Donors
• Isoantigens/immunology
• Cytokines/metabolism
• T-Lymphocytes, Regulatory/immunology

• Medical Research Council

• Humans
• B-Lymphocytes, Regulatory/immunology
• B-Lymphocytes, Regulatory/metabolism
• Animals
• Organ Transplantation/adverse effects
• Monitoring, Immunologic
• Immunotherapy/methods
• Graft Survival/immunology
• Graft Rejection/immunology
• Graft Rejection/prevention & control
• Interleukin-10/metabolism
• Interleukin-10/immunology
• Transplantation Tolerance
• Treatment Outcome
• Immunosuppressive Agents/therapeutic use

• K08 AI166021 NIAID NIH HHS

• GraB cell
• Interleukin 10
• granzyme B
• immunosuppression
• regulatory B cell

• Humans
• Mice
• Animals
• Interleukin-10/metabolism
• B-Lymphocytes, Regulatory
• Prognosis
• Cytokines/metabolism
• Inflammation/metabolism
• Immunosuppressive Agents/therapeutic use

• GMP
• HLA
• Highly sensitised
• Memory immune response
• Phase IIa
• Polyclonal expansion
• Prospective study
• Regulatory T cells
• Transplantation

• Humans
• Kidney Transplantation/adverse effects
• T-Lymphocytes, Regulatory
• Prospective Studies
• Kidney
• Immunosuppression Therapy
• HLA Antigens
• Observational Studies as Topic
• Multicenter Studies as Topic
• Clinical Trials, Phase II as Topic

• MR/T025573/1 Medical Research Council
• (Award number MR/T025573/1) Medical Research Council
• MR/S000852/1 Medical Research Council
• Department of Health

• HLA antibodies
• Kidney allograft failure
• Kidney transplantation
• Optimised immunosuppression
• Stratified medicine

• direct alloantigen recognition pathway
• donor-specific antibody
• immune monitoring
• kidney transplantation
• mixed lymphocyte reaction

• chronic allograft nephropathy
• inflammation
• lymphocytes
• transplantation

• Graft Rejection/prevention & control
• Histocompatibility
• Interferon-gamma/metabolism
• Kidney Transplantation/adverse effects
• Phenotype
• Prognosis

• MR/J006742/1 Medical Research Council
• MR/T025573/1 Medical Research Council

• accommodation
• alloantibody
• basic (laboratory) research/science
• cellular biology
• cellular transplantation (non-islet)
• translational research/science

• B cell biology
• animal models: murine
• antigen presentation/recognition
• immune regulation
• immunobiology
• immunosuppression/immune modulation
• translational research/science

Donor/recipient molecular human leukocyte antigen (HLA) mismatch predicts primary B-cell alloimmune activation, yet the impact on de novo donor-specific T-cell alloimmunity (dnDST) remains undetermined. The hypothesis of our study is that donor/recipient HLA mismatches assessed at the molecular level may also influence a higher susceptibility to the development of posttransplant primary T-cell alloimmunity. In this prospective observational study, 169 consecutive kidney transplant recipients without preformed donor-specific antibodies (DSA) and with high resolution donor/recipient HLA typing were evaluated for HLA molecular mismatch scores using different informatic algorithms [amino acid mismatch, eplet MM, and Predicted Indirectly Recognizable HLA Epitopes (PIRCHE-II)]. Primary donor-specific alloimmune activation over the first 2 years posttransplantation was assessed by means of both dnDSA and dnDST using single antigen bead (SAB) and IFN-γ ELISPOT assays, respectively. Also, the predominant alloantigen presenting pathway priming DST alloimmunity and the contribution of main alloreactive T-cell subsets were further characterized in vitro. Pretransplantation, 78/169 (46%) were DST+ whereas 91/169 (54%) DST−. At 2 years, 54/169 (32%) patients showed detectable DST responses: 23/54 (42%) dnDST and 31/54 (57%) persistently positive (persistDST+). 24/169 (14%) patients developed dnDSA. A strong correlation was observed between the three distinct molecular mismatch scores and they all accurately predicted dnDSA formation, in particular at the DQ locus. Likewise, HLA molecular incompatibility predicted the advent of dnDST, especially when assessed by PIRCHE-II score (OR 1.014 95% CI 1.001–1.03, p=0.04). While pretransplant DST predicted the development of posttransplant BPAR (OR 5.18, 95% CI=1.64–16.34, p=0.005) and particularly T cell mediated rejection (OR 5.33, 95% CI=1.45–19.66, p=0.012), patients developing dnDST were at significantly higher risk of subsequent dnDSA formation (HR 2.64, 95% CI=1.08–6.45, p=0.03). In vitro experiments showed that unlike preformed DST that is predominantly primed by CD8+ direct pathway T cells, posttransplant DST may also be activated by the indirect pathway of alloantigen presentation, and predominantly driven by CD4+ alloreactive T cells in an important proportion of patients. De novo donor-specific cellular alloreactivity seems to precede subsequent humoral alloimmune activation and is influenced by a poor donor/recipient HLA molecular matching.

• HLA mismatch
• T cell
• alloreactive
• donor-specific antibodies
• kidney transplantation

• Biomarker
• Interleukin 10 (IL-10)
• Regulatory B cells (Bregs)
• T cell immunoglobulin and mucin domain 1 (TIM-1)
• Transitional B cells (Tr B cells)
• Transplantation

• B cells
• T cells
• immunosuppression
• immunosuppression experimental
• macrophages
• novel immunosuppressants
• tolerance induction
• tolerance strategies and mechanisms

• Animals
• B-Lymphocytes, Regulatory
• Humans
• Immune Tolerance
• T-Lymphocytes, Regulatory
• Transplantation Tolerance
• Transplantation, Homologous

• 211122/Z/18/Z Wellcome Trust
• MR/N027930/1 Medical Research Council

• B lymphocytes
• chronic rejection in renal transplant
• donor specific antibody (DSA)
• kidney transplantation
• rituximab

• Adult
• B-Lymphocytes/immunology
• Female
• Graft Rejection/drug therapy
• Graft Rejection/therapy
• Graft Survival/drug effects
• Graft Survival/immunology
• Histocompatibility
• Humans
• Immunosuppression Therapy
• Immunosuppressive Agents/pharmacology
• Isoantibodies
• Kidney
• Kidney Transplantation
• Male
• Middle Aged
• Rituximab/pharmacology
• Tissue Donors

• MR/J006742/1 Medical Research Council
• MC_PC_15031 Medical Research Council
• 11/100/34 Department of Health
• MC_PC_18052 Medical Research Council
• MR/N020340/1 Medical Research Council

• HLA-DR peptide
• antigen-specific cellular response
• immunoregulation
• operational tolerance
• renal transplantation

Different patterns of plasma cytokines can be expected in the case of chronic active-antibody-mediated (cAMR) and acute cellular rejection (AR) after kidney transplantation (KTx).

• Antibody-independent B cell functions
• B cells
• Lymphoid organogenesis
• Regulatory B cells
• T cell repertoire

• Adaptive Immunity
• Animals
• Antigen Presentation
• B-Lymphocytes, Regulatory/immunology
• Cell Communication
• Graft Rejection/immunology
• Humans
• Immunity, Innate
• Immunomodulation
• Lymphocyte Activation
• Organ Transplantation
• T-Lymphocytes/immunology

• R01 AI122369 NIAID NIH HHS
• R01 OD023138 NIH HHS
• R56 AI123262 NIAID NIH HHS

• biomarker
• immune system
• kidney transplantation

• Allografts
• B-Lymphocyte Subsets
• Biomarkers
• Kidney Transplantation
• Precursor Cells, B-Lymphoid
• Transplantation, Homologous

• 11/100/34 Department of Health
• MC_PC_15031 Medical Research Council
• MR/J006742/1 Medical Research Council

To investigate the role of glutathione S-transferase T1 donor-specific T lymphocytes in plasma cell-rich rejection of liver allografts.

The study group included 22 liver transplant patients. Among them, 18 patients were mismatched for the glutathione S-transferase T1 (GSTT1) alleles (don+/rec-), and 4 were matched (don+/rec+). Seven of the mismatched patients produced anti-GSTT1 antibodies and developed plasma cell-rich rejection (former de novo immune hepatitis). For the detection of specific T lymphocytes, peripheral blood mononuclear cells were collected and stored in liquid nitrogen. The memory T cell response was studied by adding to the cell cultures to a mix of 39 custom-made, 15-mer overlapping peptides, which covered the entire GSTT1 amino acid sequence. The specific cellular response to peptides was analyzed by flow cytometry using the markers CD8, CD4, IL-4 and IFNγ.

Activation of CD8⁺ T cells with different peptides was observed exclusively in the group of patients with plasma-cell rich rejection (3 out of 7), with production of IL-4 and/or IFNγ at a rate of 1%-4.92% depending on the peptides. The CD4⁺ response was most common and not exclusive for patients with the disease, where 5 out of 7 showed percentages of activated cells from 1.24% to 31.34%. Additionally, two patients without the disease but with the mismatch had cells that became stimulated with some peptides (1.45%-5.18%). Highly unexpected was the finding of a double positive CD4⁺CD8^low T cell population that showed the highest degree of activation with some of the peptides in 7 patients with the mismatch, in 4 patients with plasma cell-rich rejection and in 3 patients without the disease. Unfortunately, CD4⁺CD8^low cells represent 1% of the total number of lymphocytes, and stimulation could not be analyzed in 9 patients due to the low number of gated cells. Cells from the 4 patients included as controls did not show activation with any of the peptides.

Patients with GSTT1 mismatch can develop a specific T-cell response, but the potential role of this response in the pathogenesis of plasma cell-rich rejection is unknown.

• Donor-specific glutathione S-transferase T1 antibodies
• Indirect presentation
• Glutathione S-transferase T1-memory T cells
• De novo immune hepatitis
• Donor/recipient mismatch

• belatacept
• costimulatory blockade
• follicular T-helper cells
• immunoglobulins
• plasmablasts
• tacrolimus
• transitional B-cells

• biomarker
• cellular assays
• immunoquiescence
• kidney transplantation
• operational tolerance

In recent years, regulatory T cells (Treg)-based immunotherapy has emerged as a promising strategy to promote operational tolerance after solid organ transplantation (SOT). However, a main hurdle for the therapeutic use of Treg in transplantation is their low frequency, particularly in non-lymphopenic hosts. We aimed to expand Treg directly in vivo and determine their efficacy in promoting donor-specific tolerance, using a stringent experimental model. Administration of the IL-2/JES6-1 immune complex at the time of transplantation resulted in significant expansion of donor-specific Treg, which suppressed alloreactive T cells. IL-2-mediated Treg expansion in combination with short-term CD154–CD40 co-stimulation blockade, but not CTLA-4 Ig or rapamycin, led to tolerance to MHC-mismatched skin grafts in non-lymphopenic mice, mainly by hindering alloreactive CD8⁺ effector T cells and the production of alloantibodies. Importantly, this treatment also allowed prolonged survival of allografts in the presence of either donor-specific or cross-reactive memory cells. However, late rejection occurred in sensitized hosts, partly mediated by activated B cells. Overall, these data illustrate the potential but also some important limitations of Treg-based therapy in clinical SOT as well as the importance of concomitant immunomodulatory strategies in particular in sensitized hosts.

• alloantibody
• memory T cells
• regulatory T cells
• tolerance
• transplantation

• B cell
• B lymphocyte
• Inflammation
• Renal interstitial fibrosis

B lymphocytes contribute to acute and chronic allograft rejection through their production of donor-specific antibodies (DSAs). In addition, B cells present allopeptides bound to self-MHC class II molecules and provide costimulation signals to T cells, which are essential to their activation and differentiation into memory T cells. On the other hand, both in laboratory rodents and patients, the concept of effector T cell regulation by B cells is gaining traction in the field of transplantation. Specifically, clinical trials using anti-CD20 monoclonal antibodies to deplete B cells and reverse DSA had a deleterious effect on rates of acute cellular rejection; a peculiar finding that calls into question a central paradigm in transplantation. Additional work in humans has characterized IL-10-producing B cells (IgM memory and transitional B cells), which suppress the proliferation and inflammatory cytokine productions of effector T cells in vitro. Understanding the mechanisms of regulating the alloresponse is critical if we are to achieve operational tolerance across transplantation. This review will focus on recent evidence in murine and human transplantation with respect to non-traditional roles for B cells in determining clinical outcomes.

• allorecognition
• antigen presentation
• autoimmune diseases
• regulatory B cells
• transplant rejection
• transplant tolerance

B cell specific immunomodulatory drugs still remain an unmet medical need. Utilisation of validated simplified in vitro models would allow readily obtaining new insights in the complexity of B cell regulation. For this purpose we investigated which human B lymphocyte stimulation assays may be ideally suited to investigate new B lymphocyte immunosuppressants. Primary polyclonal human B cells underwent in vitro stimulation and their proliferation, production of immunoglobulins (Igs) and of cytokines, and expression of cell surface molecules were analysed using various stimuli. ODN2006, a toll-like receptor 9 (TLR9) agonist, was the most potent general B cell stimulus. Subsequently, we investigated on which human B cell lines ODN2006 evoked the broadest immunostimulatory effects. The Namalwa cell line proved to be the most responsive upon TLR9 stimulation and hence may serve as a relevant, homogeneous, and stable B cell model in an in vitro phenotypic assay for the discovery of new targets and inhibitors of the B cell activation processes. As for the read-out for such screening assay, it is proposed that the expression of activation and costimulatory surface markers reliably reflects B lymphocyte activation.

Chronic antibody-mediated rejection, a common cause of renal transplant failure, has a variable clinical phenotype. Understanding why some with chronic antibody-mediated rejection progress slowly may help develop more effective therapies. B lymphocytes act as antigen-presenting cells for in vitro indirect antidonor interferon-γ production in chronic antibody-mediated rejection, but many patients retain the ability to regulate these responses. Here we test whether particular patterns of T and B cell antidonor response associate with the variability of graft dysfunction in chronic antibody-mediated rejection. Our results confirm that dynamic changes in indirect antidonor CD4⁺ T-cell responses correlate with changes in estimated glomerular filtration rates, independent of other factors. Graft dysfunction progressed rapidly in patients who developed unregulated B-cell–driven interferon-γ production. However, conversion to a regulated or nonreactive pattern, which could be achieved by optimization of immunosuppression, associated with stabilization of graft function. Functional regulation by B cells appeared to activate an interleukin-10 autocrine pathway in CD4⁺ T cells that, in turn, impacted on antigen-specific responses. Thus, our data significantly enhance the understanding of graft dysfunction associated with chronic antibody-mediated rejection and provide the foundation for strategies to prolong renal allograft survival, based on regulation of interferon-γ production.

• B lymphocyte
• ELISPOT
• chronic allograft nephropathy
• indirect alloresponses
• interferon-γ

Long-term outcomes in solid organ transplantation are constrained by the development of donor-specific alloantibodies (DSA) against human leukocyte antigen (HLA) and other targets, which elicit antibody-mediated rejection (ABMR). However, antibody-mediated graft injury represents a broad continuum, from extensive complement activation and tissue damage compromising the function of the transplanted organ, to histological manifestations of endothelial cell injury and mononuclear cell infiltration but without concurrent allograft dysfunction. In addition, while transplant recipients with DSA as a whole fare worse than those without, a substantial minority of patients with DSA do not experience poorer graft outcome. Taken together, these observations suggest that not all DSA are equally pathogenic. Antibody effector functions are controlled by a number of factors, including antibody concentration, antigen availability, and antibody isotype/subclass. Antibody isotype is specified by many integrated signals, including the antigen itself as well as from antigen-presenting cells or helper T cells. To date, a number of studies have described the repertoire of IgG subclasses directed against HLA in pretransplant patients and evaluated the clinical impact of different DSA IgG subclasses on allograft outcome. This review will summarize what is known about the repertoire of antibodies to HLA and non-HLA targets in transplantation, focusing on the distribution of IgG subclasses, as well as the general biology, etiology, and mechanisms of injury of different humoral factors.

• HLA donor-specific antibodies
• IgG subclass
• transplant

The quantification of frequency of IFN-γ–producing T cells responding to donor alloantigen using the IFN-γ enzyme linked immunosorbent spot (ELISPOT) holds potential for pretransplant and posttransplant immunological risk stratification. The effectiveness of this assay, and the ability to compare results generated by different studies, is dependent on the utilization of a standardized operating procedure (SOP). Key factors in assay standardization include the identification of primary and secondary antibody pairs, and the reading of the ELISPOT plate with a standardized automated algorithm. Here, we describe in detail, an SOP that should provide low coefficient of variation results. For multicenter trials, it is recommended that groups perform the ELISPOT assays locally but use a centralized ELISPOT reading facility, as this has been shown to be beneficial in reducing coefficient of variation between laboratories even when the SOP is strictly adhered to.

The analyses of indirect T cell responses in patients with antibody-mediated renal transplant injury by Shiu et al. emphasize the complex contribution of B cells in alloimmunity. The data suggest at least three distinct but potentially overlapping consequences of T/B cell interactions: antigen presentation by B cells, alloantibody production, and immune regulation. These multifaceted functions of B cells should be taken into consideration while developing diagnostic tools and therapeutic strategies.

• albuminuria
• chronic allograft failure
• kidney biopsy
• mortality risk
• renal
• transplant outcomes
• transplantation

• ABO-incompatible
• antibody-mediated rejection
• donor-specific antibodies
• kidney transplantation
• positive cross-match