Regulatory CD8 T cells that recognize Qa-1 expressed by CD4 T-helper cells inhibit rejection of heart allografts.

Induction of longstanding immunologic tolerance is essential for survival of transplanted organs and tissues. Despite recent advances in immunosuppression protocols, allograft damage inflicted by antibody specific for donor organs continues to represent a major obstacle to graft survival. Here we report that activation of regulatory CD8 T cells (CD8 Treg) that recognize the Qa-1 class Ib major histocompatibility complex (MHC), a mouse homolog of human leukocyte antigen-E (HLA-E), inhibits antibody-mediated immune rejection of heart allografts. We analyzed this response using a mouse model that harbors a point mutation in the class Ib MHC molecule Qa-1, which disrupts Qa-1 binding to the T cell receptor (TCR)-CD8 complex and impairs the CD8 Treg response. Despite administration of cytotoxic T lymphocyte antigen 4 (CTLA-4) immunoglobulin (Ig), Qa-1 mutant mice developed robust donor-specific antibody responses and accelerated heart graft rejection. We show that these allo-antibody responses reflect diminished Qa-1-restricted CD8 Treg-mediated suppression of host follicular helper T cell-dependent antibody production. These findings underscore the critical contribution of this Qa-1/HLA-E-dependent regulatory pathway to maintenance of transplanted organs and suggest therapeutic approaches to ameliorate allograft rejection.

Revising the Maximal Contrast Dose for Predicting Acute Kidney Injury following Coronary Intervention.

INTRODUCTION: The maximal allowable contrast dose (MACD = 5 × body weight/serum creatinine) is an empiric equation that has been used and validated in several studies to mitigate the risk of contrast-induced acute kidney injury (CI-AKI). However, coefficient 5 (referred to as factor K) was empirically devised and never disputed. The aim of this study was to refine the MACD equation for the prediction of CI-AKI following percutaneous coronary interventions (PCIs). METHODS: This is a single-center, retrospective cohort study of adults undergoing PCI. Electronic medical records were reviewed to identify patients who underwent PCI between 2010 and 2019, derived from the National Cardiovascular Data Registry Cath-PCI registry for our hospital. Factor K (defined as contrast volume × serum creatinine/body weight) was calculated for every patient. A receiver operating characteristic (ROC) curve was constructed, and the Youden index was used to identify the optimal cut-off value for factor K in predicting severe (stages 2-3) CI-AKI. RESULTS: Of the 3,506 patients undergoing PCI, 255 (7.2%) developed CI-AKI, and 68 (26.7%) of the 255 experienced severe AKI. Factor K predicted all-stage CI-AKI (area under the ROC curve 0.649; 95% CI 0.611, 0.686) but had better performance for predicting severe (stages 2-3) AKI (0.736; 95% CI 0.674, 0.800). The optimal cut-off value for factor K in predicting severe CI-AKI was 2.5, with a corresponding sensitivity of 68.7% and specificity of 70.5%. On subgroup analyses, optimal cut-off values for factor K for high-risk groups were not significantly different from those of low-risk groups. CONCLUSION: Our study indicates that factor K in the MACD equation is an independent risk factor for the development of severe CI-AKI, with an optimal cut-off value of 2.5. If our findings are validated, the MACD equation should be revised to incorporate the coefficient of 2.5 instead of 5.

Brief treatment with a highly selective immunoproteasome inhibitor promotes long-term cardiac allograft acceptance in mice.

Constitutive proteasomes (c-20S) are ubiquitously expressed cellular proteases that degrade polyubiquitinated proteins and regulate cell functions. An isoform of proteasome, the immunoproteasome (i-20S), is highly expressed in human T cells, dendritic cells (DCs), and B cells, suggesting that it could be a potential target for inflammatory diseases, including those involving autoimmunity and alloimmunity. Here, we describe DPLG3, a rationally designed, noncovalent inhibitor of the immunoproteasome chymotryptic subunit ß5i that has thousands-fold selectivity over constitutive ß5c. DPLG3 suppressed cytokine release from blood mononuclear cells and the activation of DCs and T cells, diminished accumulation of effector T cells, promoted expression of exhaustion and coinhibitory markers on T cells, and synergized with CTLA4-Ig to promote long-term acceptance of cardiac allografts across a major histocompatibility barrier. These findings demonstrate the potential value of using brief posttransplant immunoproteasome inhibition to entrain a long-term response favorable to allograft survival as part of an immunomodulatory regimen that is neither broadly immunosuppressive nor toxic.

Blocking hyaluronan synthesis alleviates acute lung allograft rejection.

Lung allograft rejection results in the accumulation of low-molecular weight hyaluronic acid (LMW-HA), which further propagates inflammation and tissue injury. We have previously shown that therapeutic lymphangiogenesis in a murine model of lung allograft rejection reduced tissue LMW-HA and was associated with improved transplant outcomes. Herein, we investigated the use of 4-Methylumbelliferone (4MU), a known inhibitor of HA synthesis, to alleviate acute allograft rejection in a murine model of lung transplantation. We found that treating mice with 4MU from days 20 to 30 after transplant was sufficient to significantly improve outcomes, characterized by a reduction in T cell-mediated lung inflammation and LMW-HA content and in improved pathology scores. In vitro, 4MU directly attenuated activation, proliferation, and differentiation of naive CD4+ T cells into Th1 cells. As 4MU has already been demonstrated to be safe for human use, we believe examining 4MU for the treatment of acute lung allograft rejection may be of clinical significance.

Mechanical Prosthetic Aortic Valve Thrombosis Complicated by an Acute Coronary Syndrome During Fibrinolysis.

A 70-year-old man with mechanical aortic and mitral valves was admitted with progressive shortness of breath. He was found to have thrombosis of the aortic valve prosthesis. Treatment with intravenous thrombolysis was complicated by an acute coronary syndrome related to coronary embolism. The patient was successfully managed conservatively with long-term anticoagulation. An algorithm for the management of coronary embolism is suggested. (Level of Difficulty: Advanced.).

Intraparenchymal hemorrhage and cerebral venous thrombosis in an adult with congenital porencephalic cyst presenting for generalized tonic-clonic seizures.

Prothrombotic conditions are known risk factors for porencephalic cyst formation and cerebral vein thrombosis. Intracerebral hemorrhage is a potential complication of a cerebral vein thrombosis. Porencephaly is a risk factor for intracerebral hemorrhage and cerebral vein thrombosis formation. We present the case of an adult patient with a past medical history of epilepsy and congenital porencephalic cyst with de novo mutation of the COL4A1 gene who presented for episodes of generalized tonic-clonic seizure after a substantial symptom-free period. A brain CT scan showed an intracerebral hemorrhage with porencephalic cyst and superior sagittal sinus thrombosis despite negative thrombophilia work-up. A CT perfusion study, CT angiography, and brain MRI confirmed the diagnosis. The cause-and-effect relationship between porencephalic cysts, cerebral venous thrombosis, and intracerebral hemorrhage is still not clear in the literature.

Regulatory T cells engineered with TCR signaling-responsive IL-2 nanogels suppress alloimmunity in sites of antigen encounter.

Adoptive cell transfer of ex vivo expanded regulatory T cells (Tregs) has shown immense potential in animal models of auto- and alloimmunity. However, the effective translation of such Treg therapies to the clinic has been slow. Because Treg homeostasis is known to require continuous T cell receptor (TCR) ligation and exogenous interleukin-2 (IL-2), some investigators have explored the use of low-dose IL-2 injections to increase endogenous Treg responses. Systemic IL-2 immunotherapy, however, can also lead to the activation of cytotoxic T lymphocytes and natural killer cells, causing adverse therapeutic outcomes. Here, we describe a drug delivery platform, which can be engineered to autostimulate Tregs with IL-2 in response to TCR-dependent activation, and thus activate these cells in sites of antigen encounter. To this end, protein nanogels (NGs) were synthesized with cleavable bis(N-hydroxysuccinimide) cross-linkers and IL-2/Fc fusion (IL-2) proteins to form particles that release IL-2 under reducing conditions, as found at the surface of T cells receiving stimulation through the TCR. Tregs surface-conjugated with IL-2 NGs were found to have preferential, allograft-protective effects relative to unmodified Tregs or Tregs stimulated with systemic IL-2. We demonstrate that murine and human NG-modified Tregs carrying an IL-2 cargo perform better than conventional Tregs in suppressing alloimmunity in murine and humanized mouse allotransplantation models. In all, the technology presented in this study has the potential to improve Treg transfer therapy by enabling the regulated spatiotemporal provision of IL-2 to antigen-primed Tregs.

Pulse oximeter ingestion in a psychotic patient.

Psychotic conditions such as schizophrenia, bipolar disorder, major depressive disorder, and polysusbstance abuse are risk factors for foreign body ingestion. A foreign body can include sharp objects that lead to serious complications. In this case report, we present a patient with a history of psychosis who ingested a pulse oximeter in a suicidal attempt. The pulse oximeter passed uneventfully with no interventions needed, and was followed by a serial of abdominal imaging.

Unusual presentation of urban leptospirosis complicated by a septic shock.

Leptospirosis, an infectious zoonosis, is common to tropical areas. The clinical presentation varies from flu-like symptoms to a serious presentation called Weil's syndrome. Fever and conjunctival suffusion are present in the majority of patients. This case report describes a resident of New York City who presented initially with gastroenteritis symptoms without fever or conjunctival suffusion to develop septic shock before being diagnosed with leptospirosis.

Human regulatory T cells undergo self-inflicted damage via granzyme pathways upon activation.

Tregs hold great promise as a cellular therapy for multiple immunologically mediated diseases, given their ability to control immune responses. The success of such strategies depends on the expansion of healthy, suppressive Tregs ex vivo and in vivo following the transfer. In clinical studies, levels of transferred Tregs decline sharply in the blood within a few days of the transfer. Tregs have a high rate of apoptosis. Here, we describe a new mechanism of Treg self-inflicted damage. We show that granzymes A and -B (GrA and GrB), which are highly upregulated in human Tregs upon stimulation, leak out of cytotoxic granules to induce cleavage of cytoplasmic and nuclear substrates, precipitating apoptosis in target cells. GrA and GrB substrates were protected from cleavage by inhibiting granzyme activity in vitro. Additionally, we show - by using cytometry by time of flight (CYTOF) - an increase in GrB-expressing Tregs in the peripheral blood and renal allografts of transplant recipients undergoing rejection. These GrB-expressing Tregs showed an activated phenotype but were significantly more apoptotic than non-GrB expressing Tregs. This potentially novel finding improves our understanding of Treg survival and suggests that manipulating Gr expression or activity might be useful for designing more effective Treg therapies.

Integrated Kidney Exosome Analysis for the Detection of Kidney Transplant Rejection.

Kidney transplant patients require life-long surveillance to detect allograft rejection. Repeated biopsy, albeit the clinical gold standard, is an invasive procedure with the risk of complications and comparatively high cost. Conversely, serum creatinine or urinary proteins are noninvasive alternatives but are late markers with low specificity. We report a urine-based platform to detect kidney transplant rejection. Termed iKEA (integrated kidney exosome analysis), the approach detects extracellular vesicles (EVs) released by immune cells into urine; we reasoned that T cells, attacking kidney allografts, would shed EVs, which in turn can be used as a surrogate marker for inflammation. We optimized iKEA to detect T-cell-derived EVs and implemented a portable sensing system. When applied to clinical urine samples, iKEA revealed high level of CD3-positive EVs in kidney rejection patients and achieved high detection accuracy (91.1%). Fast, noninvasive, and cost-effective, iKEA could offer new opportunities in managing transplant recipients, perhaps even in a home setting.