Allorecognition and the alloresponse: clinical implications

Usefulness of Diffusion-Weighted Imaging in Evaluating Acute Cellular Rejection and Monitoring Treatment Response in Liver Transplant Recipients

Acute cellular rejection (ACR) is a significant immune issue among recipients following liver transplantation. Although diffusion-weighted magnetic resonance imaging (DWI) is widely used for diagnosing liver disease, it has not yet been utilized for monitoring ACR in patients after liver transplantation. Therefore, the aim of this study was to evaluate the efficacy of DWI in monitoring treatment response among recipients with ACR. This study enrolled 25 recipients with highly suspected ACR rejection, and all subjects underwent both biochemistry and DWI scans before and after treatment. A pathological biopsy was performed 4 to 24 h after the first MRI examination to confirm ACR and degree of rejection. All patients were followed up and underwent a repeated MRI scan when their liver function returned to the normal range. After data acquisition, the DWI data were post-processed to obtain the apparent diffusion coefficient (ADC) map on a voxel-by-voxel basis. Five regions of interest were identified on the liver parenchyma to measure the mean ADC values from each patient. Finally, the mean ADC values and biochemical markers were statistically compared between ACR and non-ACR groups. A receiver operating characteristic (ROC) curve was constructed to evaluate the performance of the ADC and biochemical data in detecting ACR, and correlation analysis was used to understand the relationship between the ADC values, biochemical markers, and the degree of rejection. The histopathologic results revealed that 20 recipients had ACR, including 10 mild, 9 moderate, and 1 severe rejection. The results demonstrated that the ACR patients had significantly lower hepatic ADC values than those in patients without ACR. After treatment, the hepatic ADC values in ACR patients significantly increased to levels similar to those in non-ACR patients with treatment. The ROC analysis showed that the sensitivity and specificity for detecting ACR were 80% and 95%, respectively. Furthermore, the correlation analysis revealed that the mean ADC value and alanine aminotransferase level had strong and moderate negative correlation with the degree of rejection, respectively (r = -0.72 and -0.47). The ADC values were useful for detecting hepatic ACR and monitoring treatment response after immunosuppressive therapy.

Impact of the HLA Immunopeptidome on Survival of Leukemia Patients After Unrelated Donor Transplantation

PURPOSE

Immunopeptidome divergence between mismatched HLA-DP is a determinant of T-cell alloreactivity and clinical tolerability after fully HLA-A, -B, -C, -DRB1, -DQB1 matched unrelated donor hematopoietic cell transplantation (UD-HCT). Here, we tested this concept in HLA-A, -B, and -C disparities after single class I HLA-mismatched UD-HCT.

PATIENTS AND METHODS

We studied 2,391 single class I HLA-mismatched and 14,426 fully HLA-matched UD-HCT performed between 2008 and 2018 for acute leukemia or myelodysplastic syndromes. Hierarchical clustering of experimentally determined peptide-binding motifs (PBM) was used as a proxy for immunopeptidome divergence of HLA-A, -B, or -C disparities, allowing us to classify 1,629/2,391 (68.1%) of the HLA-mismatched UD-HCT as PBM-matched or PBM-mismatched. Risks associated with PBM-matching status were assessed by Cox proportional hazards models, with overall survival (OS) as the primary end point.

RESULTS

Relative to full matches, bidirectional or unidirectional PBM mismatches in graft-versus-host (GVH) direction (PBM-GVH mismatches, 60.7%) were associated with significantly lower OS (hazard ratio [HR], 1.48; P < .0001), while unidirectional PBM mismatches in host-versus-graft direction or PBM matches (PBM-GVH matches, 39.3%) were not (HR, 1.13; P = .1017). PBM-GVH mismatches also had significantly lower OS than PBM-GVH matches in direct comparison (HR, 1.32; P = .0036). The hazards for transplant-related mortality and acute and chronic graft-versus-host disease but not relapse increased stepwise from full HLA matches to single PBM-GVH matches, and single PBM-GVH mismatches. A webtool for PBM-matching of single class I HLA-mismatched donor-recipient pairs was developed.

CONCLUSION

PBM-GVH mismatches inform mortality risks after single class I HLA-mismatched UD-HCT, suggesting that prospective consideration of directional PBM-matching status might improve outcome. These findings highlight immunopeptidome divergence between mismatched HLA as a driver of clinical tolerability in UD-HCT.

Risk factors for acute rejection in liver transplantation and its impact on the outcomes of recipients

OBJECTIVE

To determine the risk factors for acute rejection in liver transplantation and its impact on the outcomes of the recipients.

METHODS

Clinicopathological data of 290 patients who underwent liver transplantation from January 2012 to December 2021 at our center were retrospectively evaluated. Patients were grouped into an acute rejection (AR) group and a normal (NM) group based on the confirmed histopathological diagnosis of acute rejection. Univariate and multivariate logistic regression were used to determine the risk factors for acute rejection.

RESULTS

244 patients were included in the study. Acute rejection occurred in 27 (11.1%) of the patients. Warm ischemia time (P = 0.137), cold ischemia time (P = 0.064) and chronic liver failure (P = 0.001) were potential risk factors for acute rejection. Chronic liver failure (P < 0.001, OR = 8.22, 95% CI = 2.47-27.32) was the independent risk factor. There was no significant difference in overall survival between recipients with acute rejection and those without it (P = 0.985). The 1-, 3- and 5-year overall survival in the NM group was 98.1%, 85.7% and 78.6% respectively vs 88.9%, 82.5% and 82.5% respectively in the AR group.

CONCLUSION

Acute rejection does not appear to affect the long-term survival of the recipients. Only chronic liver failure was an independent risk factor for acute rejection. Our findings further illustrate that contradictions still exist on which factors influence acute rejection in liver transplant recipients.

SUMMARY

Clinicopathological data of 290 liver transplant recipients at our center between January 2012 and December 2021 were retrospectively evaluated to determine the risk factors for acute rejection and its impact on the outcomes of the recipients. 244 patients were included in the analysis. 27 of the 244 experienced acute rejection. Propensity score matching was performed to reduce the confounding effect. Patients were assigned to an acute rejection group (n = 27) and a normal group (n = 54). Chronic liver failure (P < 0.001, OR = 8.22, 95% CI = 2.47-27.32) was the determined to be independent risk factor for acute rejection. Acute rejection did not appear to affect the long-term survival of the recipients and there was no significant difference in overall survival between the patients with acute rejection and those without it.

Polymeric nanomedicines for the treatment of hepatic diseases

The liver is an important organ in the human body and performs many functions, such as digestion, detoxification, metabolism, immune responses, and vitamin and mineral storage. Therefore, disorders of liver functions triggered by various hepatic diseases, including hepatitis B virus infection, nonalcoholic steatohepatitis, hepatic fibrosis, hepatocellular carcinoma, and transplant rejection, significantly threaten human health worldwide. Polymer-based nanomedicines, which can be easily engineered with ideal physicochemical characteristics and functions, have considerable merits, including contributions to improved therapeutic outcomes and reduced adverse effects of drugs, in the treatment of hepatic diseases compared to traditional therapeutic agents. This review describes liver anatomy and function, and liver targeting strategies, hepatic disease treatment applications and intrahepatic fates of polymeric nanomedicines. The challenges and outlooks of hepatic disease treatment with polymeric nanomedicines are also discussed.

Human Hepatic CD56bright NK Cells Display a Tissue-Resident Transcriptional Profile and Enhanced Ability to Kill Allogenic CD8+ T Cells

Liver-resident CD56^brightCD16^- natural killer (NK) cells are enriched in the human liver and are phenotypically distinct from their blood counterparts. Although these cells are capable of rapid cytotoxic effector activity, their functional role remains unclear. We hypothesise that they may contribute to immune tolerance in the liver during transplantation. RNA sequencing was carried out on FACS sorted NK cell subpopulations from liver perfusates (n=5) and healthy blood controls (n=5). Liver-resident CD56^brightCD16^+/- NK cells upregulate genes associated with tissue residency. They also upregulate expression of CD160 and LY9, both of which encode immune receptors capable of activating NK cells. Co-expression of CD160 and Ly9 on liver-resident NK cells was validated using flow cytometry. Hepatic NK cell cytotoxicity against allogenic T cells was tested using an in vitro co-culture system of liver perfusate-derived NK cells and blood T cells (n=10-13). In co-culture experiments, hepatic NK cells but not blood NK cells induced significant allogenic T cell death (p=0.0306). Allogenic CD8⁺ T cells were more susceptible to hepatic NK cytotoxicity than CD4⁺ T cells (p<0.0001). Stimulation of hepatic CD56^bright NK cells with an anti-CD160 agonist mAb enhanced this cytotoxic response (p=0.0382). Our results highlight a role for donor liver NK cells in regulating allogenic CD8⁺ T cell activation, which may be important in controlling recipient CD8⁺ T cell-mediated rejection post liver-transplant.

Biological therapies in patients with liver disease: are they really lifesavers?

INTRODUCTION

The liver plays a key role in the setting of immune tolerance. Targeting antigens for presentation by antigen-presenting cells in the liver can induce immune tolerance to either autoantigens from the liver itself or organs outside of the liver. Despite its non-conventional capacity for tolerance induction, the liver remains a target organ for autoimmune diseases. Whereas chronic inflammation and intra-hepatic immuno-suppressive microenvironment occurring during liver fibrosis lead to hepatocellular carcinoma. Monoclonal antibodies have revolutionized the therapeutic strategies of many autoimmune diseases and some cancers.

AREAS COVERED

We review data from literature regarding the safety and efficacy of biologics in treating hepatobiliary autoimmune diseases and primary liver cancers. Furthermore, we describe their potential use in the setting of liver transplants and their main immune-related liver adverse events.

EXPERT OPINION

Biological therapies have changed the natural history of main autoimmune diseases and solid cancers. Compared to other organs and disease settings, the liver lags behind in biologics and their applications. The development of novel diagnostic and therapeutic strategies based on the immunological and antigenic characteristics of the hepatobiliary system could reduce mortality and transplant rates linked to chronic liver diseases.

Mutant B2M-HLA-E and B2M-HLA-G fusion proteins protects universal chimeric antigen receptor-modified T cells from allogeneic NK cell-mediated lysis

Recent studies have indicated the antitumor activity and reduced allogeneic response of universal chimeric antigen receptor-modified T (UCAR T) cells lacking endogenous T cell receptors and beta-2 microglobulin (B2M) generated using gene-editing technologies. However, these cells are vulnerable to lysis by allogeneic natural killer (NK) cells due to their lack of human leukocyte antigen (HLA) class I molecule expression. Here, constitutive expression of mutant B2M-HLA-E (mBE) and B2M-HLA-G (mBG) fusion proteins in anti-CD19 UCAR T (UCAR T-19) cells was conducted to protect against allogeneic NK cell-mediated lysis. The ability of cells expressing mBE or mBG to resist NK cell-mediated lysis was observed in gene-edited Jurkat CAR19 cells. UCAR T-19 cells constitutively expressing the mBE and mBG fusion proteins were manufactured and showed effective and specific anti-tumor activity. Constitutive expression of the mBE and mBG fusion proteins in UCAR T-19 cells prevented allogeneic NK cell-mediated lysis. In addition, these cells were not recognizable by allogeneic T cells. Additional experiments, including those in animal models and clinical trials, are required to evaluate the safety and efficacy of UCAR T-19 cells that constitutively express mBE and mBG.

Study of Cell Viability and Etiology of Contamination in Decalcified Bone Allograft: A Pilot Study

BACKGROUND

Bone allografts can elicit immune responses which is correlated with the presence of Human Leukocyte Antigen (HLA) and cellular DNA. It also has risk of causing occult infection arising out of contamination during its processing and storage. The presence of immunogenic materials like cells, cellular remnants and DNA in a decalcified bone allograft during different phases of processing has never been studied. Present study was conducted to explore- the cell viability using routine Hematoxylin and Eosin, presence of DNA using Feulgen staining and etiology of contamination in decalcified bone allograft during procurement, demineralization and ethanol preservation.

METHODS

The harvested bones from patients undergoing hemireplacement/THR/TKR were processed to prepare decalcified bone allografts. The samples during procurement (A), HCL treatment (B) and ethanol preservation (C) were sent for histopathological analysis (number of osteocytes in the maximum density field under 40x and the cells demonstrating presence of DNA on feulgen stain) and microbiological assessment (aerobic/anaerobic/fungal cultures).

RESULTS

Histopathological study demonstrated the presence of osteocytes and other cells like bone marrow, adipocytes, endothelial cells in the decal bone allograft. The average number of osteocytes gradually decreased from 55.47, 9.6, 0.86 in sample A, B, C, respectively. Feulgen staining confirmed the presence of DNA in osteocytes and other cells which decreased both qualitatively and quantitatively in subsequent stages of processing. Rate of contamination demonstrated at the procurement was 6.67% (Staphylococcus aureus). After treatment with HCl (demineralisation), 7.14% of non-contaminated allografts were found contaminated (Staphylococcus epidermidis). None of the remaining 13 non-contaminated allografts showed contamination after storage in ethanol. Overall 13% of the patients had positive cultures on microbiological assessment.

CONCLUSION

The population of osteocytes in the harvested bone reduced significantly after processing with HCl and ethanol preservation. Presence of DNA, demonstrated by using Feulgen staining, was observed in bone marrow cells, adipocytes along with osteocytes which showed quantitative reduction on processing. Hence, antigenicity, conferred by cells and their DNA, reduced significantly after processing of decal bone. Contamination rate of banked decalcified allograft was 13%. Thus, culture and sensitivity tests should be carried out at each step of processing of decal bone allograft.

Donor/Recipient HLA Molecular Mismatch Scores Predict Primary Humoral and Cellular Alloimmunity in Kidney Transplantation

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.

Chronic Histologic Changes Are Present Regardless of HLA Mismatches: Evidence from HLA Identical Living Donor Kidney Transplants

BACKGROUND

At 5 and 10 years after kidney transplantation, chronic histologic changes such as arteriolar hyalinosis and mesangial expansion are common, however, determining etiology is difficult. We compared surveillance biopsies in living donor kidney transplants (LDKTx) from HLA matched siblings (termed HLA-identical (HLA-ID)) to HLA non-ID to investigate which histologic changes were likely due to alloimmune injury and which were due to non-alloimmune injury.

METHODS

We performed a retrospective, cohort study comparing HLA-ID sibling LDKTx (n=175) to HLA non-ID LDKTx (n=175; matched for age, sex and year of transplant +/- 2 years) performed at a single institution from 03/1999 to 11/2018.

RESULTS

Baseline characteristics and maintenance immunosuppression were similar. Mortality rates were similar, but in the HLA-ID group, 10-year death-censored graft survival was higher (93.8% vs 80.9% HLA non-ID LDKTx, p<0.001), rejection rates were lower (after 1 year 9.6% vs 27.1%; p<0.001) and Banff inflammation scores including glomerulitis and peritubular capillaritis were lower on surveillance biopsies at 1, 5 and 10 years. In contrast, chronic Banff scores (interstitial fibrosis, arteriolar hyalinosis, mesangial expansion, etc.) were similar in prevalence and severity on surveillance biopsies at 1, 5 and 10 years.

CONCLUSIONS

HLA-ID LDKTx have less inflammation and less transplant glomerulopathy, but most chronic histologic changes were similar to less-well matched LDKTx. We conclude that these types of chronic changes are not associated with HLA mismatches and may be due to non-immunologic causes (hypertension, obesity, etc.) suggesting that new management approaches to prevent these lesions may be needed.

Suppression of liver transplant rejection by anti-donor MHC antibodies via depletion of donor immunogenic dendritic cells

BACKGROUND

We previously found two distinct passenger dendritic cell (DC) subsets in the rat liver that played a central role in the liver transplant rejection. In addition, a tolerance-inducing protocol, donor-specific transfusion (DST), triggered systemic polytopical production of depleting alloantibodies to donor class I MHC (MHCI) antigen (DST-antibodies).

METHODS

We examined the role of DST-antibodies in the trafficking of graft DC subsets and the alloresponses in a rat model. We also examined an anti-donor class II MHC (MHCII) antibody that recognizes donor DCs more selectively.

RESULTS

Preoperative transfer of DST-antibodies or DST pretreatment eliminated all passenger leukocytes, including both DC subsets and depleted the sessile DCs in the graft to ~20% of control. The CD172a+CD11b/c+ immunogenic subset was almost abolished. The intrahost direct or semi-direct allorecognition pathway was successfully blocked, leading to a significant suppression of the CD8+ T-cell response in the recipient lymphoid organs and the graft with delayed graft rejection. Anti-donor MHCII antibody had similar effects without temporary graft damage. Although DST pretreatment had a priming effect on the proliferative response of recipient regulatory T cells, DST-primed sera and the anti-donor MHCII antibody did not.

CONCLUSION

DST-antibodies and anti-donor MHCII antibodies could suppress the CD8+ T-cell-mediated liver transplant rejection by depleting donor immunogenic DCs, blocking the direct or semi-direct pathways of allorecognition. Donor MHCII-specific antibodies may be applicable as a selective suppressant of anti-donor immunity for clinical liver transplantation without the cellular damage of donor MHCII- graft cells and recipient cells.

First Human Leucocyte Antigen (HLA) Response and Safety Evaluation of Fibrous Demineralized Bone Matrix in a Critical Size Femoral Defect Model of the Sprague-Dawley Rat

Treatment of large bone defects is one of the great challenges in contemporary orthopedic and traumatic surgery. Grafts are necessary to support bone healing. A well-established allograft is demineralized bone matrix (DBM) prepared from donated human bone tissue. In this study, a fibrous demineralized bone matrix (f-DBM) with a high surface-to-volume ratio has been analyzed for toxicity and immunogenicity. f-DBM was transplanted to a 5-mm, plate-stabilized, femoral critical-size-bone-defect in Sprague-Dawley (SD)-rats. Healthy animals were used as controls. After two months histology, hematological analyses, immunogenicity as well as serum biochemistry were performed. Evaluation of free radical release and hematological and biochemical analyses showed no significant differences between the control group and recipients of f-DBM. Histologically, there was no evidence of damage to liver and kidney and good bone healing was observed in the f-DBM group. Reactivity against human HLA class I and class II antigens was detected with mostly low fluorescence values both in the serum of untreated and treated animals, reflecting rather a background reaction. Taken together, these results provide evidence for no systemic toxicity and the first proof of no basic immunogenic reaction to bone allograft and no sensitization of the recipient.

Strategies for Genetically Engineering Hypoimmunogenic Universal Pluripotent Stem Cells

Despite progress in developing cell therapies, such as T cell or stem cell therapies to treat diseases, immunoincompatibility remains a major barrier to clinical application. Given the fact that a host's immune system may reject allogeneic transplanted cells, methods have been developed to genetically modify patients' primary cells. To advance beyond this time-consuming and costly approach, recent research efforts focus on generating universal pluripotent stem cells to benefit a broader spectrum of patients. In this review, we first summarize current achievements to harness immunosuppressive mechanisms in cells to reduce immunogenicity. Then, we discuss several recent studies demonstrating the feasibility of genetically modifying pluripotent stem cells to escape immune attack and summarize the methods to evaluate hypoimmunogenicity. Although challenges remain, progress to develop genetically engineered universal pluripotent stem cells holds the promise of expediting their use in future gene and cell therapeutics and regenerative medicine.

Natural Killer Cell Alloreactivity Against Human Induced Pluripotent Stem Cells and Their Neuronal Derivatives into Dopaminergic Neurons

In recent years, great hope has arisen surrounding human stem cells, particularly human induced pluripotent stem (hiPS) cells, as nearly all human tissues can be derived from hiPS cells, using a specific protocol. Therefore, hiPS cells can be a source for replacing defective tissues and make up for the lack of organ donors. However, the alloreactivity of hiPS cells and their derivatives in the context of transplantation remain unclear. Although immunosuppressive drugs can inhibit the T cell compartment, these drugs inhibit partially or not at all natural killer (NK) cells activity. Therefore, the alloreactivity of NK cells against transplanted cells remains to be established. To partially answer this question, we choose, as a model, the potential of cellular therapy for Parkinson's disease (PD). First, we established the in vitro derivation of hiPS cells into mature dopaminergic (mDOPA) neurons, going through an intermediate step called neurosphere (NS) cells. These different cells population were cultured with or without interferon gamma (IFN-γ). They were characterized phenotypically regarding their morphology, and the expression of specific ligands for NK cell receptors expressed by these cells types was investigated. NK cells were isolated from the peripheral blood of healthy donors and cultured in the presence of interleukin 15, to be activated. To test NK cell alloreactivity, a cytotoxic assay was performed with hiPS cells, NS cells, and mDOPA neurons (IFN-γ treated or not) cocultured with allogenic NK cells. Our results show that allogenic NK cells kill hiPS cells (IFN-γ treated or not), but IFN-γ-treated NS cells were protected from killing by allogenic NK cells, compared with untreated NS cells. Finally, mDOPA neurons (IFN-γ treated or not) were partially protected against allogenic NK cell killing. These results indicate that derivatives of hiPS cells, especially NS cells, could be a good product for allogenic transplantation in cellular therapy for PD.

Novel immunological approach to asses donor reactivity of transplant recipients using a humanized mouse model

In organ transplantation, a reproducible and robust immune-monitoring assay has not been established to determine individually tailored immunosuppressants (IS). We applied humanized mice reconstituted with human (hu-) peripheral blood mononuclear cells (PBMCs) obtained from living donor liver transplant recipients to evaluate their immune status. Engraftment of 2.5 × 10⁶ hu-PBMCs from healthy volunteers and recipients in the NSG mice was achieved successfully. The reconstituted lymphocytes consisted mainly of hu-CD3⁺ lymphocytes with predominant CD45RA^-CD62L^lo T_EM and CCR6^-CXCR3⁺CD4⁺ Th1 cells in hu-PBMC-NSG mice. Interestingly, T cell allo-reactivity of hu-PBMC-NSG mice was amplified significantly compared with that of freshly isolated PBMCs (p < 0.05). Furthermore, magnified hu-T cell responses to donor antigens (Ag) were observed in 2/10 immunosuppressed recipients with multiple acute rejection (AR) experiences, suggesting that the immunological assay in hu-PBMC-NSG mice revealed hidden risks of allograft rejection by IS. Furthermore, donor Ag-specific hyporesponsiveness was maintained in recipients who had been completely weaned off IS (n = 4), despite homeostatic proliferation of hu-T cells in the hu-PBMC-NSG mice. The immunological assay in humanized mice provides a new tool to assess recipient immunity in the absence of IS and explore the underlying mechanisms to maintaining operational tolerance.

Application of PLGA nano/microparticle delivery systems for immunomodulation and prevention of allotransplant rejection

INTRODUCTION

Allograft transplantation is an effective end-point therapy to replace the function of an impaired organ. The main problem associated with allotransplantation is the induction of immune responses that results in acute and chronic graft rejection. To modulate the response of the immune system, transplant recipients generally take high dose immunosuppressant drugs for life. These drugs are associated with serious side effects such as infection with opportunistic pathogens and the development of neoplasia.

AREAS COVERED

We reviewed the obstacles to successful transplantation and PLGA-based strategies to reduce immune-mediated allograft rejection.

EXPERT OPINION

Biomaterial-based approaches using micro- and nanoparticles such as poly (lactic-co-glycolic acid) (PLGA) can be used to achieve controlled release of drugs. This approach decreases the required effective dose of drugs and enables local delivery of these agents to specific tissues and cells, whilst decreasing systemic effects.

Novel Targeting to XCR1+ Dendritic Cells Using Allogeneic T Cells for Polytopical Antibody Responses in the Lymph Nodes

Vaccination strategy that induce efficient antibody responses polytopically in most lymph nodes (LNs) against infections has not been established yet. Because donor-specific blood transfusion induces anti-donor class I MHC antibody production in splenectomized rats, we examined the mechanism and significance of this response. Among the donor blood components, T cells were the most efficient immunogens, inducing recipient T cell and B cell proliferative responses not only in the spleen, but also in the peripheral and gut LNs. Donor T cells soon migrated to the splenic T cell area and the LNs, with a temporary significant increase in recipient NK cells. XCR1⁺ resident dendritic cells (DCs), but not XCR1⁻ DCs, selectively phagocytosed donor class I MHC⁺ fragments after 1 day. After 1.5 days, both DC subsets formed clusters with recipient CD4⁺ T cells, which proliferated within these clusters. Inhibition of donor T cell migration or depletion of NK cells by pretreatment with pertussis toxin or anti-asialoGM₁ antibody, respectively, significantly suppressed DC phagocytosis and subsequent immune responses. Three allogeneic strains with different NK activities had the same response but with different intensity. Donor T cell proliferation was not required, indicating that the graft vs. host reaction is dispensable. Intravenous transfer of antigen-labeled and mitotic inhibitor-treated allogeneic, but not syngeneic, T cells induced a polytopical antibody response to labeled antigens in the LNs of splenectomized rats. These results demonstrate a novel mechanism of alloresponses polytopically in the secondary lymphoid organs (SLOs) induced by allogeneic T cells. Donor T cells behave as self-migratory antigen ferries to be delivered to resident XCR1⁺ DCs with negligible commitment of migratory DCs. Allogeneic T cells may be clinically applicable as vaccine vectors for polytopical prophylactic antibody production even in asplenic or hyposplenic individuals.

IL17A and IL17F genes polymorphisms are associated with histopathological changes in transplanted kidney

Background

Interleukin 17 is a proinflammatory cytokine involved in immune response after allograft transplantation. IL-17 family of proinflammatory cytokines includes IL-17A and IL-17F. Previous studies have demonstrated that the rs2275913 IL17A and the rs11465553 IL17F gene polymorphism are associated with kidney allograft function. Because of the association between these polymorphisms and post-transplant immune response, we assume that these single nucleotide polymorphisms may affect morphological structure of transplanted kidney.

The aim of this study was to examine the association of rs2275913 IL17A and rs2397084, rs11465553 and rs763780 IL17F gene polymorphisms with histopathological changes in transplanted kidney biopsies such as: glomerulitis, tubulitis, arteritis, cell infilitration and fibrosis.

Methods

The study enrolled 82 patients after renal graft transplantation in whom a kidney biopsy was performed because of impaired graft function. The rs2397084 T > C (Glu126Gly), rs11465553 G > A (Val155Ile) and rs763780 T > C (His167Arg) polymorphisms within the IL17F gene and the rs2275913 A > G (− 197 A > G) polymorphism within the IL17A gene promoter were genotyped using TaqMan genotyping assays on a 7500 FAST Real-Time PCR System (Applied Biosystems, USA).

Results

There was a significant association between the rs2275913 IL17A gene polymorphism and the grade of tubulitis, which was more severe among patients with the A allele, compared to recipients with the GG genotype (GG vs. AG + AA, P = 0.02), and with the grade of arteriolar hyaline thickening and mesangial matrix increase, which were more severe among patients with the G allele compared to recipients with the AA genotype (AA vs. AG + GG, P = 0.01 and P = 0.04, respectively). Tubular atrophy and interstitial fibrosis were more severe among individuals with the C allele at the rs763780 IL17F gene polymorphism (TT vs. TC, P = 0.09 and P = 0.017, respectively). However, it should be taken into account that the statistical significance was achieved without correction for multiple testing, and no significant association would remain significant after such correction.

Conclusions

The results of this study may suggest a possible association between the rs2275913 IL17A and rs2275913 IL17A gene polymorphisms and some histopathological changes in transplanted kidney biopsies.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1308-z) contains supplementary material, which is available to authorized users.

Determination of HLA-A, -B, -C, -DRB1 and -DQB1 allele and haplotype frequencies in heart failure patients

Aims

Cell therapy can be used to repair functionally impaired organs and tissues in humans. Although autologous cells have an immunological advantage, it is difficult to obtain high cell numbers for therapy. Well‐characterized banks of cells with human leukocyte antigens (HLA) that are representative of a given population are thus needed. The present study investigates the HLA allele and haplotype frequencies in a cohort of heart failure (HF) patients.

Methods and results

We carried out the HLA typing and the allele and haplotype frequency analysis in 247 ambulatory HF patients. We determined HLA class I (A, B, and C) and class II (DRB1 and DQB1) using next‐generation sequencing technology. The allele frequencies were obtained using Python for Population Genomics (PyPop) software, and HLA haplotypes were estimated using HaploStats. A total of 30 HLA‐A, 56 HLA‐B, 23 HLA‐C, 36 HLA‐DRB1, and 15 HLA‐DQB1 distinct alleles were identified within the studied cohort. The genotype frequencies of all five HLA loci were in Hardy–Weinberg equilibrium. We detected differences in HLA allele frequencies among patients when the etiological cause of HF was considered. There were a total of 494 five‐loci haplotypes, five of which were present six or more times. Moreover, the most common estimated HLA haplotype was HLA‐A*01:01, HLA‐B*08:01, HLA‐C*07:01, HLA‐DRB1*03:01, and HLA‐DQB1*02:01 (6.07% haplotype frequency per patient). Remarkably, the 11 most frequent haplotypes would cover 31.17% of the patients of the cohort in need of allogeneic cell therapy.

Conclusions

Our findings could be useful for improving allogeneic cell administration outcomes without concomitant immunosuppression.

Prevention of relapse after allogeneic hematopoietic cell transplantation by donor and cell source selection

Allogeneic hematopoietic cell transplantation (HCT) is the most established form of cancer immunotherapy and has been successfully applied for the treatment and cure of otherwise lethal neoplastic blood disorders. Cancer immune surveillance is mediated to a large extent by alloreactive T and natural killer (NK) cells recognizing genetic differences between patient and donor. Profound insights into the biology of these effector cells has been obtained over recent years and used for the development of innovative strategies for intelligent donor selection, aiming for improved graft-versus-leukemia effect without unmanageable graft-versus-host disease. The cellular composition of the stem cell source plays a major role in modulating these effects. This review summarizes the current state-of the-art of donor selection according to HLA, NK alloreactivity and stem cell source.

WITHDRAWN: Response to letter to the editor: The sole and combined effect of simvastatin and platelet rich fibrin as a filling material in induced bone defect in tibia of albino rats

The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.bone.2019.01.007. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Belatacept for maintenance immunosuppression in cardiothoracic transplantation: The potential frontier

Current immunosuppressive regimens with calcineurin inhibitors have improved the management of patients after transplantation. However, their adverse effects are linked to increased morbidity and limit the long-term survival of heart and lung transplant recipients. Belatacept, a costimulation inhibitor interfering with the interaction between CD28 on T cells and the B7 ligands on antigen presenting cells, has shown success and is currently approved for use in renal transplant recipients. Furthermore, it lacks many of the cardiovascular, metabolic, neurologic, and renal adverse of effects of calcineurin inhibitors that have the largest impact on long-term survival in cardiothoracic transplant. Additionally, it requires no therapeutic drug monitoring and is only administered once a month. Limitations to belatacept use have been observed that must be considered when comparing immunosuppression options. Despite this, maintenance immunosuppression with belatacept has the potential to improve outcomes in cardiothoracic transplant recipients, as it has with kidney transplant recipients. However, no large clinical trials investigating belatacept for maintenance immunosuppression in heart and lung transplant recipients exist. There is a large need for focused research of belatacept in cardiothoracic transplantation. Belatacept is a viable treatment option for maintenance immunosuppression, and it is reasonable to pursue more evidence in cardiothoracic transplant recipients.

Detection of major histocompatibility complex molecules in processed allogeneic bone blocks for use in alveolar ridge reconstruction

OBJECTIVES

Because processed allogenic bone blocks contain remnants of cells and other organic material, the present study examined the putative presence of major histocompatibility complex (MHC) molecules in protein extracts derived from processed allogeneic bone blocks.

STUDY DESIGN

Protein content and the immunogenic potential of 3 different processed allografts (Osteograft, DIZG, Berlin, Germany; Caput femoris, DIZG, Berlin, Germany; Human Spongiosa, Charité Tissue Bank, Berlin, Germany) were assessed by protein extraction and analysis of the presence of MHC class 1 and 2 molecules prior to grafting. MHC concentration was measured by using enzyme-linked immunosorbent assay.

RESULTS

Protein content in the allograft materials varied between 0.87 and 1.61 µg protein/mg. In the allograft Human Spongiosa, no MHC was detected, whereas in the allogeneic bone blocks Osteograft and Caput femoris MHC 1 (0.04-0.037 ng/mg graft material) and in Osteograft MHC class 2 molecules were detectable.

CONCLUSIONS

The results of the present study suggest that despite thorough processing, a potential antigenicity of allografts is not eliminated. MHC molecules in allografts may sensitize the immune system.

Immunomodulatory activity of glycodelin: implications in allograft rejection

Glycodelin is an immunomodulator, indispensable for the maintenance of pregnancy in humans. The glycoprotein induces apoptosis in activated CD4⁺ T cells, monocytes and natural killer (NK) cells, and suppresses the activity of cytotoxic T cells, macrophages and dendritic cells. This study explores the immunosuppressive property of glycodelin for its possible use in preventing graft rejection. Because glycodelin is found only in certain primates, the hypothesis was investigated in an allograft nude mouse model. It is demonstrated that treatment of alloactivated mononuclear cells with glycodelin thwarts graft rejection. Glycodelin decreases the number of activated CD4⁺ and CD8⁺ cells and down-regulates the expression of key proteins known to be involved in graft demise such as granzyme-B, eomesodermin (EOMES), interleukin (IL)-2 and proinflammatory cytokines [tumour necrosis factor (TNF)-α and IL-6], resulting in a weakened cell-mediated immune response. Immunosuppressive drugs for treating allograft rejection are associated with severe side effects. Glycodelin, a natural immunomodulator in humans, would be an ideal alternative candidate.

Acute and Chronic Rejection After Liver Transplantation: What A Clinician Needs to Know

While antibody mediated hyper-acute vasculitic rejection is rare in liver transplant recipients, acute and chronic rejection have clinical significance. The liver allograft behaves differently to other solid organ transplants as acute rejection generally does not impair graft survival and chronic rejection (CR) is uncommon. The incidence of acute and chronic rejection has declined in current era due to improved immunosuppressive regimens. Acute rejection generally improves with steroid boluses and steroid resistant rejection is uncommon. CR may improve with escalation of immunosuppression or may result in irreversible loss of graft function leading to retransplantation or death. The current review discusses diagnosis and management of acute and chronic liver allograft rejection.

HLA-DP in unrelated hematopoietic cell transplantation revisited: challenges and opportunities

When considering HLA-matched hematopoietic cell transplantation (HCT), sibling and unrelated donors (UDs) are biologically different because UD-HCT is typically performed across HLA-DP disparities absent in sibling HCT. Mismatched HLA-DP is targeted by direct alloreactive T cell responses with important implications for graft-versus-host disease and graft-versus-leukemia. This concise review details special features of HLA-DP as model antigens for clinically permissive mismatches mediating limited T-cell alloreactivity with minimal toxicity, and describes future avenues for their exploitation in cellular immunotherapy of malignant blood disorders.

Alloimmune T cells in transplantation

Alloimmune T cells are central mediators of rejection and graft-versus-host disease in both solid organ and hematopoietic stem cell transplantation. Unique among immune responses in terms of its strength and diversity, the T cell alloresponse reflects extensive genetic polymorphisms between allogeneic donors and recipients, most prominently within the major histocompatibility complex (MHC), which encodes human leukocyte antigens (HLAs) in humans. The repertoire of alloreactive T cell clones is distinct for every donor-recipient pair and includes potentially thousands of unique HLA/peptide specificities. The extraordinary magnitude of the primary alloresponse and diversity of the T cell population mediating it have presented technical challenges to its study in humans. High-throughput T cell receptor sequencing approaches have opened up new possibilities for tackling many fundamental questions about this important immunologic phenomenon.

Antibody-Mediated Rejection After Liver Transplant

Antibody-mediated rejection (AMR) in liver transplants is a field in its infancy compared with its allograft cohorts of the kidney and lung. Acute AMR is diagnosed based on specific clinical and histopathologic criteria: serum donor specific antibodies, C4d staining, histopathologic findings on liver biopsy, and exclusion of other entities. In contrast, the histologic features of chronic AMR are not as specific and it is a more challenging diagnosis to make. Treatments of acute and chronic AMR include some combination of steroids, immune-modulating agents, intravenous immunoglobulin, plasmapheresis, and proteasome inhibitors.

Chimeric Antigen Receptors: A Cell and Gene Therapy Perspective

Chimeric antigen receptors (CARs) are synthetic receptors that reprogram T lymphocytes to target chosen antigens. The targeting of CD19, a cell surface molecule expressed in the vast majority of leukemias and lymphomas, has been successfully translated in the clinic, earning CAR therapy a special distinction in the selection of "cancer immunotherapy" by Science as the breakthrough of the year in 2013. CD19 CAR therapy is predicated on advances in genetic engineering, T cell biology, tumor immunology, synthetic biology, target identification, cell manufacturing sciences, and regulatory compliance-the central tenets of CAR therapy. Here, we review two of these foundations: the genetic engineering approaches and cell types to engineer.

Can immunosuppression be stopped after liver transplantation?

Liver transplantation has improved dramatically over the past three decades, mainly as a result of advances in surgical techniques and management of post-transplant complications. The focus has now turned towards rescuing additional organs in the face of scarce organ supply, or prevention of long-term toxicity associated with immunosuppression. The liver appears to be privileged in terms of immune tolerance, with a low incidence of antibody-mediated rejection, which is in sharp contrast to other solid organ transplants, such as kidney, lung, and heart transplants. However, tolerogenic processes remain poorly understood, and strategies for complete drug withdrawal should be selected carefully to avoid graft rejection. In this Review, we summarise the current understanding of liver-specific immune responses and provide an outlook on future approaches.

Old game, new players: Linking classical theories to new trends in transplant immunology

The evolutionary emergence of an efficient immune system has a fundamental role in our survival against pathogenic attacks. Nevertheless, this same protective mechanism may also establish a negative consequence in the setting of disorders such as autoimmunity and transplant rejection. In light of the latter, although research has long uncovered main concepts of allogeneic recognition, immune rejection is still the main obstacle to long-term graft survival. Therefore, in order to define effective therapies that prolong graft viability, it is essential that we understand the underlying mediators and mechanisms that participate in transplant rejection. This multifaceted process is characterized by diverse cellular and humoral participants with innate and adaptive functions that can determine the type of rejection or promote graft acceptance. Although a number of mediators of graft recognition have been described in traditional immunology, recent studies indicate that defining rigid roles for certain immune cells and factors may be more complicated than originally conceived. Current research has also targeted specific cells and drugs that regulate immune activation and induce tolerance. This review will give a broad view of the most recent understanding of the allogeneic inflammatory/tolerogenic response and current insights into cellular and drug therapies that modulate immune activation that may prove to be useful in the induction of tolerance in the clinical setting.

Integration of a CD19 CAR into the TCR Alpha Chain Locus Streamlines Production of Allogeneic Gene-Edited CAR T Cells

Adoptive cellular therapy using chimeric antigen receptor (CAR) T cell therapies have produced significant objective responses in patients with CD19⁺ hematological malignancies, including durable complete responses. Although the majority of clinical trials to date have used autologous patient cells as the starting material to generate CAR T cells, this strategy poses significant manufacturing challenges and, for some patients, may not be feasible because of their advanced disease state or difficulty with manufacturing suitable numbers of CAR T cells. Alternatively, T cells from a healthy donor can be used to produce an allogeneic CAR T therapy, provided the cells are rendered incapable of eliciting graft versus host disease (GvHD). One approach to the production of these cells is gene editing to eliminate expression of the endogenous T cell receptor (TCR). Here we report a streamlined strategy for generating allogeneic CAR T cells by targeting the insertion of a CAR transgene directly into the native TCR locus using an engineered homing endonuclease and an AAV donor template. We demonstrate that anti-CD19 CAR T cells produced in this manner do not express the endogenous TCR, exhibit potent effector functions in vitro, and mediate clearance of CD19⁺ tumors in an in vivo mouse model.

TGF-β affinity-bound to a macroporous alginate scaffold generates local and peripheral immunotolerant responses and improves allocell transplantation

Enhancing vascularization of cell-transplantation devices is necessary for maintaining cell viability and integration within the host, but it also increases the risk of allograft rejection. Here, we investigated the feasibility of generating an immunoregulatory environment in a highly vascularized macroporous alginate scaffold by affinity-binding of the transforming growth factor-β (TGF-β) in a manner mimicking its binding to heparan sulfate. Using this device to transplant allofibroblasts under the kidney capsule resulted in the induction of local and peripheral TGF-β-dependent immunotolerance, characterized by higher frequency of immature dendritic cells and regulatory T cells within the device and by markedly reduced allofibroblast-specific T-cell response in the spleen, thereby increasing the viability of the transplanted cells. Culturing whole splenocytes in the TGF-β-bound scaffold indicated that the regulatory function of TGF-β is IL-10-dependent. We thus demonstrate a novel platform for transplantation devices, designed to promote an immunoregulatory microenvironment suitable for cell transplantation and autoimmune regulation.

STATEMENT OF SIGNIFICANCE

Allogeneic cell graft transplantation is a potentially optimal treatment for many clinical deficiencies. It is yet challenging to overcome chronic rejection without compromising host immunity to pathogens. We present the features and function of a cell transplantation device designed based on the principle of affinity binding of angiogenic and immunoregulatory factors to extracellular matrix in aim to achieve sustained release of these factors. We show that presentation of these factors in such manner generates the infrastructure for device vascularization and induces profound local allocell-specific tolerance, which then evokes peripheral T-cell tolerance. The tolerance is antigen specific, does not cause immune deficits and may thus serve to improve allocell survival as well as a platform to mitigate pathogenic autoimmunity.

Effects of methoxypoly (Ethylene glycol) mediated immunocamouflage on leukocyte surface marker detection, cell conjugation, activation and alloproliferation

Tissue rejection occurs subsequent to the recognition of foreign antigens via receptor-ligand contacts between APC (antigen presenting cells) and T cells, resulting in initialization of signaling cascades and T cell proliferation. Bioengineering of donor cells by the covalent attachment of methoxypolyethylene glycol (mPEG) to membrane proteins (PEGylation) provides a novel means to attenuate these interactions consequent to mPEG-induced charge and steric camouflage. While previous studies demonstrated that polymer-mediated immunocamouflage decreased immune recognition both in vitro and in vivo, these studies monitored late events in immune recognition and activation such as T cell proliferation. Consequently little information has been provided concerning the early cellular events governing this response. Therefore, the effect of PEGylation was assessed by examining initial cell-cell interactions, changes to activation pathways, and apoptosis to understand the role that each may play in the decreased proliferative response observed in modified cells during the course of a mixed lymphocyte reaction (MLR). The mPEG-modified T cells resulted in significant immunocamouflage of lymphocyte surface proteins and decreased interactions with APC. Furthermore, mPEG-MLR exhibited decreased NFκB pathway activation, while exhibiting no significant differences in degree of cell death compared to the control MLR. These results suggest that PEGylation may prevent the direct recognition of foreign alloantigens by decreasing the stability and duration of initial cell-cell interactions.

Autoimmune Liver Disease Post-Liver Transplantation: A Summary and Proposed Areas for Future Research

Autoimmune liver diseases (AILD) are rare diseases with a reported prevalence of less than 50 per 100 000 population. As the research landscape and our understanding of AILDs and liver transplantation evolves, there remain areas of unmet needs. One of these areas of unmet needs is prevention of disease recurrence after liver transplantation. Disease recurrence is not an insignificant event because allograft loss with the need for retransplantation can occur. Patients transplanted for AILD are more likely to experience acute rejection compared to those transplanted for non-AILD, and the reason(s) behind this observation is unclear. Tasks for the future include a better understanding of the pathogenesis of AILD, definition of the precise pathogenetic mechanisms of recurrent AILD, and development of strategies that can identify recipients at risk for disease recurrence. Importantly, the role of crosstalk between alloimmune responses and autoimmune responses in AILD is an important area that needs further study.

This article reviews the relevant literature of de novo autoimmune hepatitis, recurrent autoimmune hepatitis, recurrent primary sclerosing cholangitis, and recurrent primary biliary cirrhosis in terms of the clinical entity, the scientific advancements, and future scientific goals to enhance our understanding of these diseases.

A review of the relevant literature of de novo autoimmune hepatitis, recurrent autoimmune hepatitis, recurrent primary sclerosing cholangitis, and recurrent primary biliary cirrhosis in terms of the clinical entity, the scientific advancements and future scientific goals to enhance our understanding of these diseases.

Targeting the Innate Immune Response to Improve Cardiac Graft Recovery after Heart Transplantation: Implications for the Donation after Cardiac Death

Heart transplantation (HTx) is the ultimate treatment for end-stage heart failure. The number of patients on waiting lists for heart transplants, however, is much higher than the number of available organs. The shortage of donor hearts is a serious concern since the population affected by heart failure is constantly increasing. Furthermore, the long-term success of HTx poses some challenges despite the improvement in the management of the short-term complications and in the methods to limit graft rejection. Myocardial injury occurs during transplantation. Injury initiated in the donor as result of brain or cardiac death is exacerbated by organ procurement and storage, and is ultimately amplified by reperfusion injury at the time of transplantation. The innate immune system is a mechanism of first-line defense against pathogens and cell injury. Innate immunity is activated during myocardial injury and produces deleterious effects on the heart structure and function. Here, we briefly discuss the role of the innate immunity in the initiation of myocardial injury, with particular focus on the Toll-like receptors and inflammasome, and how to potentially expand the donor population by targeting the innate immune response.

Pathogenesis of the intravertebral vacuum of Kümmell's disease

In this review, we explored the progress of the pathogenesis of Kümmell's disease intravertebral vacuum. Using different expressions of the same disease including 'Kümmell's disease', 'avascular necrosis after vertebral compression fracture (VCF)', 'post-traumatic vertebral osteonecrosis', 'vertebral pseudarthrosis', 'intravertebral vacuum (cleft or gas)', 'delayed vertebral collapse', 'VCF nonunion', and by conducting a search of the PubMed database, we analyzed the results to examine the pathogenesis of the intravertebral vacuum of Kümmell's disease after referring to pertinent literature on intravertebral vacuum of ischemic necrosis after VCF, and exploring the progress of pathogenesis of this disease. A number of discrepancies were identified within the pathogenesis of the intravertebral vacuum after VCF. There were statements such as avascular necrosis of the vertebral body, bone biomechanics, gas forming and other types of claims, all of which obtained clinical and biomechanical supporting evidence. Collectively, most of the researchers believe that Kümmell vertebral fracture syndrome was the comprehensive effect of multiple factors including osteoporosis, avascular necrosis of the vertebral body, and biomechanical changes following fracture. However, there are a number of discrepancies to be resolved and future studies are therefore needed.

New cell sources for T cell engineering and adoptive immunotherapy

The promising clinical results obtained with engineered T cells, including chimeric antigen receptor (CAR) therapy, call for further advancements to facilitate and broaden their applicability. One potentially beneficial innovation is to exploit new T cell sources that reduce the need for autologous cell manufacturing and enable cell transfer across histocompatibility barriers. Here we review emerging T cell engineering approaches that utilize alternative T cell sources, which include virus-specific or T cell receptor-less allogeneic T cells, expanded lymphoid progenitors, and induced pluripotent stem cell (iPSC)-derived T lymphocytes. The latter offer the prospect for true off-the-shelf, genetically enhanced, histocompatible cell therapy products.

Strategies for improving the efficacy of donor lymphocyte infusion following stem cell transplantation

Donor lymphocyte infusion (DLI) is an effective immunotherapeutic approach with significant activity in the treatment and prevention of relapse after allogeneic stem cell transplantation. DLI is associated with significant toxicity mainly due to graft-versus-host disease. Moreover, DLI does not produce durable responses in aggressive malignancies like acute leukemia. Improvement in DLI efficacy requires dissociation of graft-versus-leukemia effect from graft-versus-host disease. Minor histocompatibility antigens with tissue restriction and leukemia or tumor-associated antigens represent ideal antigenic targets. A brief overview of the existing methods of DLI administration is the topic of this article. T cells transduced with genes encoding for T-cell receptors with reactivity against minor histocompatibility antigens or leukemia-associated antigens is a promising option.

Current trends in platelet transfusions practice: The role of ABO-RhD and human leukocyte antigen incompatibility

Platelet transfusions have contributed to the revolutionary modern treatment of hypoproliferative thrombocytopenia. Despite the long-term application of platelet transfusion in therapeutics, all aspects of their optimal use (i.e., in cases of ABO and/or Rh (D incompatibility) have not been definitively determined yet. We reviewed the available data on transfusion practices and outcome in ABO and RhD incompatibility and platelet refractoriness due to anti-human leukocyte antigen (HLA) antibodies. Transfusion of platelets with major ABO-incompatibility is related to reduced posttransfusion platelet (PLT) count increments, compared to ABO-identical and minor, but still are equally effective in preventing clinical bleeding. ABO-minor incompatible transfusions pose the risk of an acute hemolytic reaction of the recipient that is not always related to high anti-A, B donor titers. ABO-identical PLT transfusion seems to be the most effective and safest therapeutic strategy. Exclusive ABO-identical platelet transfusion policy could be feasible, but alternative approaches could facilitate platelet inventory management. Transfusion of platelets from RhD positive donors to RhD negative patients is considered to be effective and safe though is associated with low rate of anti-D alloimmunization due to contaminating red blood cells. The prevention of D alloimmunization is recommended only for women of childbearing age. HLA alloimmunization is a major cause of platelet refractoriness. Managing patients with refractoriness with cross-matched or HLA-matched platelets is the current practice although data are still lacking for the efficacy of this practice in terms of clinical outcome. Leukoreduction contributes to the reduction of both HLA and anti-D alloimmunization.

The Human Mesenchymal Stromal Cell-Derived Osteocyte Capacity to Modulate Dendritic Cell Functions Is Strictly Dependent on the Culture System

In vitro differentiation of mesenchymal stromal cells (MSC) into osteocytes (human differentiated osteogenic cells, hDOC) before implantation has been proposed to optimize bone regeneration. However, a deep characterization of the immunological properties of DOC, including their effect on dendritic cell (DC) function, is not available. DOC can be used either as cellular suspension (detached, Det-DOC) or as adherent cells implanted on scaffolds (adherent, Adh-DOC). By mimicking in vitro these two different routes of administration, we show that both Det-DOC and Adh-DOC can modulate DC functions. Specifically, the weak downregulation of CD80 and CD86 caused by Det-DOC on DC surface results in a weak modulation of DC functions, which indeed retain a high capacity to induce T-cell proliferation and to generate CD4⁺CD25⁺Foxp3⁺ T cells. Moreover, Det-DOC enhance the DC capacity to differentiate CD4⁺CD161⁺CD196⁺ Th17-cells by upregulating IL-6 secretion. Conversely, Adh-DOC strongly suppress DC functions by a profound downregulation of CD80 and CD86 on DC as well as by the inhibition of TGF-β production. In conclusion, we demonstrate that different types of DOC cell preparation may have a different impact on the modulation of the host immune system. This finding may have relevant implications for the design of cell-based tissue-engineering strategies.

Biomarkers of acute rejection following cardiac transplantation

Cardiac transplantation can be a life-saving treatment for selected patients with heart failure. However, despite advances in immunosuppressive therapy, acute allograft rejection remains a significant cause of morbidity and mortality. The current 'gold standard' for rejection surveillance is endomyocardial biopsy, which aims to identify episodes of rejection prior to development of clinical manifestations. This is an invasive technique with a risk of false-positive and false-negative results. Consequently, a wide variety of noninvasive alternatives have been investigated for their potential role as biomarkers of rejection. This article reviews the evidence behind proposed alternatives such as imaging techniques, electrophysiological parameters and peripheral blood markers, and highlights the potential future role for biomarkers in cardiac transplantation as an adjunct to biopsy.

Immunogenetic factors in the selection of cord blood units for transplantation: current search strategies and future perspectives

Hematopoietic stem cell transplantation is currently used as a curative treatment for patients with malignant and non-malignant hematologic diseases. Human leukocyte antigen (HLA) matching is a major determinant for hematopoietic stem cell transplantation outcome. For patients lacking a fully HLA-matched donor, umbilical cord blood (UCB) units are alternative sources of hematopoietic stem cells because UCB transplantation allows a less stringent HLA matching. However, selection of the optimal UCB units remains challenging. The current UCB donor selection strategies are based on both cell dose and HLA matching. This Review focuses on the immunogenetic factors that influence UCB donor selection and highlights the future perspectives in UCB donor search.