Iron status influences mitochondrial disease progression in Complex I-deficient mice.

Mitochondrial dysfunction caused by aberrant Complex I assembly and reduced activity of the electron transport chain is pathogenic in many genetic and age-related diseases. Mice missing the Complex I subunit NADH dehydrogenase [ubiquinone] iron-sulfur protein 4 (NDUFS4) are a leading mammalian model of severe mitochondrial disease that exhibit many characteristic symptoms of Leigh Syndrome including oxidative stress, neuroinflammation, brain lesions, and premature death. NDUFS4 knockout mice have decreased expression of nearly every Complex I subunit. As Complex I normally contains at least 8 iron-sulfur clusters and more than 25 iron atoms, we asked whether a deficiency of Complex I may lead to iron perturbations, thereby accelerating disease progression. Consistent with this, iron supplementation accelerates symptoms of brain degeneration in these mice, while iron restriction delays the onset of these symptoms, reduces neuroinflammation, and increases survival. NDUFS4 knockout mice display signs of iron overload in the liver including increased expression of hepcidin and show changes in iron-responsive element-regulated proteins consistent with increased cellular iron that were prevented by iron restriction. These results suggest that perturbed iron homeostasis may contribute to pathology in Leigh Syndrome and possibly other mitochondrial disorders.

Iron is a mineral that contributes to many vital body functions. But as people age, it accumulates in many organs, including the liver and the brain. Excess iron accumulation is linked to age-related diseases like Parkinson's disease. Too much iron may contribute to harmful chemical reactions in the body. Usually, the body has systems in place to mitigate this harm, but these mechanisms may fail as people age. Uncontrolled iron accumulation may damage essential proteins, DNA and fats in the brain. These changes may kill brain cells causing neurodegenerative diseases like Parkinson's disease. Mitochondria, the cell's energy-producing factories, use and collect iron inside cells. As people age, mitochondria fail, which is also linked with age-related diseases. It has been unclear if mitochondrial failure may also contribute to iron accumulation and associated diseases like Parkinson's. Kelly et al. show that mitochondrial dysfunction causes iron accumulation and contributes to neurodegeneration in mice. In the experiments, Kelly et al. used mice with a mutation in a key-iron processing protein in mitochondria. These mice develop neurodegenerative symptoms and die early in life. Feeding the mice a high-iron diet accelerated the animals' symptoms. But providing them with an iron-restricted diet slowed their symptoms and extended their lives. Low-iron diets also slowed iron accumulation in the animal's liver and reduced brain inflammation. The experiments suggest that mitochondrial dysfunction contributes to both iron overload and brain degeneration. The next step for scientists is understanding the processes leading to mitochondrial dysfunction and iron accumulation. Then, scientists can determine if they can develop treatments targeting these processes. This research might lead to new treatments for Parkinson's disease or other age-related conditions caused by iron overload.

A Pragmatic Randomized Trial Comparing Surgical Clipping and Endovascular Treatment of Unruptured Intracranial Aneurysms.

BACKGROUND AND PURPOSE: Surgical clipping and endovascular treatment are commonly used in patients with unruptured intracranial aneurysms. We compared the safety and efficacy of the 2 treatments in a randomized trial. MATERIALS AND METHODS: Clipping or endovascular treatments were randomly allocated to patients with one or more 3- to 25-mm unruptured intracranial aneurysms judged treatable both ways by participating physicians. The study hypothesized that clipping would decrease the incidence of treatment failure from 13% to 4%, a composite primary outcome defined as failure of aneurysm occlusion, intracranial hemorrhage during follow-up, or residual aneurysms at 1 year, as adjudicated by a core lab. Safety outcomes included new neurologic deficits following treatment, hospitalization of >5 days, and overall morbidity and mortality (mRS > 2) at 1 year. There was no blinding. RESULTS: Two hundred ninety-one patients were enrolled from 2010 to 2020 in 7 centers. The 1-year primary outcome, ascertainable in 290/291 (99%) patients, was reached in 13/142 (9%; 95% CI, 5%-15%) patients allocated to surgery and in 28/148 (19%; 95% CI, 13%-26%) patients allocated to endovascular treatments (relative risk: 2.07; 95% CI, 1.12-3.83; P = .021). Morbidity and mortality (mRS >2) at 1 year occurred in 3/143 and 3/148 (2%; 95% CI, 1%-6%) patients allocated to surgery and endovascular treatments, respectively. Neurologic deficits (32/143, 22%; 95% CI, 16%-30% versus 19/148, 12%; 95% CI, 8%-19%; relative risk: 1.74; 95% CI, 1.04-2.92; P = .04) and hospitalizations beyond 5 days (69/143, 48%; 95% CI, 40%-56% versus 12/148, 8%; 95% CI, 5%-14%; relative risk: 0.18; 95% CI, 0.11-0.31; P < .001) were more frequent after surgery. CONCLUSIONS: Surgical clipping is more effective than endovascular treatment of unruptured intracranial aneurysms in terms of the frequency of the primary outcome of treatment failure. Results were mainly driven by angiographic results at 1 year.

Should stents be used in the treatment of ruptured intracranial aneurysms?

The indications for endovascular coiling of intracranial aneurysms continue to expand. This is due, in part, to the development of intracranial specific stents which permit remodelling of complex aneurysm necks. While this approach has several advantages in the setting of unruptured aneurysms, certain challenges, in particular the requirement of concomitant antiplatelet medication, may limit its use in treatment of ruptured intracranial aneurysms. These devices can be used safely and effectively in the treatment of selected ruptured aneurysms. One must weigh the potential hemorrhagic complications against the benefits of stent assisted coiling and the disadvantages of alternative approaches.

A Uniform Description of Perioperative Brain MRI Findings in Infants with Severe Congenital Heart Disease: Results of a European Collaboration.

BACKGROUND AND PURPOSE: A uniform description of brain MR imaging findings in infants with severe congenital heart disease to assess risk factors, predict outcome, and compare centers is lacking. Our objective was to uniformly describe the spectrum of perioperative brain MR imaging findings in infants with congenital heart disease. MATERIALS AND METHODS: Prospective observational studies were performed at 3 European centers between 2009 and 2019. Brain MR imaging was performed preoperatively and/or postoperatively in infants with transposition of the great arteries, single-ventricle physiology, or left ventricular outflow tract obstruction undergoing cardiac surgery within the first 6 weeks of life. Brain injury was assessed on T1, T2, DWI, SWI, and MRV. A subsample of images was assessed jointly to reach a consensus. RESULTS: A total of 348 MR imaging scans (180 preoperatively, 168 postoperatively, 146 pre- and postoperatively) were obtained in 202 infants. Preoperative, new postoperative, and cumulative postoperative white matter injury was identified in 25%, 30%, and 36%; arterial ischemic stroke, in 6%, 10%, and 14%; hypoxic-ischemic watershed injury in 2%, 1%, and 1%; intraparenchymal cerebral hemorrhage, in 0%, 4%, and 5%; cerebellar hemorrhage, in 6%, 2%, and 6%; intraventricular hemorrhage, in 14%, 6%, and 13%; subdural hemorrhage, in 29%, 17%, and 29%; and cerebral sinovenous thrombosis, in 0%, 10%, and 10%, respectively. CONCLUSIONS: A broad spectrum of perioperative brain MR imaging findings was found in infants with severe congenital heart disease. We propose an MR imaging protocol including T1-, T2-, diffusion-, and susceptibility-weighted imaging, and MRV to identify ischemic, hemorrhagic, and thrombotic lesions observed in this patient group.

Contrasuppression in autoimmunity. Abnormal contrasuppression facilitates expression of nephritogenic effector T cells and interstitial nephritis in kdkd mice.

We have used the murine model of spontaneous autoimmune interstitial nephritis in kdkd mice to examine the importance of abnormal immunoregulation in the expression of disease. T cells from naive congenic CBA/Ca mice suppress both histologic renal injury in the kdkd strain as well as the DTH reactivity to CBA/Ca renal tubular antigens mediated by lymphocytes from nephritic kdkd mice. These antigen-specific suppressor T cells are Lyt-2+, L3T4+, I-Jk+, genetically dominant and I-Jk restricted. Unfractionated spleen cells from young, prenephritic kdkd mice also demonstrate such suppressor function. Shortly preceding disease onset, however, net suppression is functionally bypassed by emergent contrasuppressor T cells. These regulatory cells are also Lyt-2+ and I-Jk+, and adhere both to the Vicia Villosa lectin and CBA/Ca TBM. By admixing these contrasuppressor cells with spleen cells from non-disease-prone CBA/Ca mice we were able to demonstrate the presence of DTH-reactive and nephritogenic effector cells in the latter population. Such nephritogenic effector cells could also be simply demonstrated after depletion of the suppressor cells with anti-I-Jk mAbs and complement. These findings support a role for contrasuppressor cells in the abrogation of tolerance to parenchymal self-antigens.

Tolerance to parenchymal self. Regulatory role of major histocompatibility complex-restricted, OX8+ suppressor T cells specific for autologous renal tubular antigen in experimental interstitial nephritis.

BN rats develop interstitial nephritis after immunization with rabbit, but not rat renal tubular antigen. Using RT1n rat strains that differentially express tubular antigen, we investigated the unresponsiveness of BN rats to BN tubular antigen (BN-TBM) using delayed-type hypersensitivity (DTH) responses to BN-TBM as a measure of cell-mediated immunity. Our results indicate that rat strains expressing tubular antigen respond to immunization with BN-TBM with the clonal expansion of antigen-specific, cyclophosphamide-sensitive, OX8+, MHC-restricted suppressor T cells. Such suppression appears to be relevant to the maintenance of tolerance to parenchymal self, since chronic cyclophosphamide therapy abrogates suppression and results in significant interstitial nephritis.

Antiidiotypic immunity in interstitial nephritis. II. Rats developing anti-tubular basement membrane disease fail to make an antiidiotypic regulatory response: the modulatory role of an RT7.1+, OX8- suppressor T cell mechanism.

Antiidiotypic immunity can successfully inhibit the development of antitubular basement membrane (alpha TBM) disease that produces interstitial nephritis. Rats normally immunized to produce disease, however, do not develop this regulatory and protective antiidiotypic effect. The failure to see such a regulatory response is functionally related to the influence of a nonspecific, RT7.1+, OX8-suppressor T cell that appears shortly after immunization. While this suppressor cell system can partially reduce the intensity of disease, it also limits the host's ability to specifically regulate the alpha TBM immune response and, hypothetically, leaves the disease process in an operationally active mode.

T cells reactive to an inducible heat shock protein induce disease in toxin-induced interstitial nephritis.

T cells reactive against immunodominant regions of inducible heat shock proteins (HSPs) have been identified in the chronic inflammatory lesions of several experimental autoimmune diseases. Since HSPs are known to be induced by a number of renal tubular epithelial cell toxins associated with chronic interstitial nephritis, we investigated the relevance of HSP expression and T cell reactivity to HSP70 in a model of progressive inflammatory interstitial nephritis. Chronic administration of cadmium chloride (CdCl2) to SJL/J mice induces HSP70 expression in renal tubular cells 4-5 wk before the development of interstitial mononuclear cell infiltrates. CdCl2 also induces HSP70 expression in cultured tubular epithelial cells from SJL/J mice. CD4+, TCR-alpha/beta+ T cell lines specific for an immunodominant HSP peptide are cytotoxic to heat stressed or CdCl2-treated renal tubular cells. Such HSP-reactive T cells mediate an inflammatory interstitial nephritis after adoptive transfer to CdCl2-treated mice at a time when immunoreactive HSP70 is detectable in the kidneys, but before the development of interstitial mononuclear cell infiltrates. T cells isolated from the nephritic kidneys of mice treated with CdCl2 for 13 wk are also cytotoxic to heat shocked or cadmium-treated tubular cells. These kidney-derived T cells additionally induced interstitial nephritis after passive transfer, indicating their pathogenic significance. Our studies strongly support a role for HSP-reactive T cells in CdCl2-induced interstitial nephritis and suggest that the induction of HSPs in the kidney by a multitude of "non-immune" events may initiate or facilitate inflammatory damage by HSP-reactive lymphocytes.

Adjuvant immunotherapy is dependent on inducible nitric oxide synthase.

Rodents immunized with complete Freund's adjuvant (CFA) are resistant to subsequent attempts to induce autoimmune disease, while animals immunized with incomplete Freund's adjuvant (IFA) remain susceptible. Mycobacterial extracts can stimulate inducible nitric oxide synthase (NOS2) gene transcription. Robust expression of NOS2 has been linked to suppression of T cell proliferation and alterations in immune responses. Our studies investigated the hypothesis that the immunoprotective effect of CFA before immunization requires functional NOS2. NOS2 gene expression is chronically elevated in lymph nodes and spleens of CFA-immunized mice. Maximal expression of NOS2 after CFA immunization requires the presence of functional type I tumor necrosis factor alpha receptor (TNFR1) and interferon gamma. Groups of nontreated and CFA-preimmunized male C57BL/6J or C57BL/6NOS2(-/)- mice were immunized with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 in CFA to induce experimental allergic encephalomyelitis (EAE). Wild-type C57BL/6J mice were protected from the development of symptoms of EAE, while the NOS2(-/)- mice failed to be protected. NOS2-dependent effects of CFA included an augmentation of the MOG-specific IgG1 response, a decrease in interleukin 6 production by MOG-reactive lymphocytes, and a marked decrease in mononuclear cell infiltrates in the central nervous system. These studies support the hypothesis that CFA immunization modulates immune responses through a nitric oxide-dependent mechanism.

Impact of the BioFire FilmArray gastrointestinal panel on patient care and infection control.

OBJECTIVES: Conventional routine PCR testing for gastrointestinal infections is generally based on pathogen related panels specifically requested by clinicians and can be erroneous and time consuming. The BioFire FilmArray gastrointestinal (GI) panel combines 22 pathogens into a single cartridge-based test on a random-access system, thereby reducing the turnaround time to less than 2 hours. We described the clinical impact of implementing the BioFire FilmArray on patients with gastroenteritis in our hospital. METHODS: Patients attending a Dutch tertiary care center (Radboud University Medical Center), from whom stool samples were obtained, were eligible for inclusion. The clinicians selected one or a combination of different routinely performed PCR panels (bacterial panel, viral panel, clostridium testing, and three parasitic panels) based on clinical history and symptoms. All samples were in parallel tested with the FilmArray. We retrospectively collected patient data regarding infection control and patient management to assess the potential impact of implementing the FilmArray. RESULTS: In total 182 patients were included. Routine PCR detected one or more pathogens in 52 (28.6%) patients compared to 72 (39.6%) using the FilmArray. Turnaround time (including transport) decreased from median 53 hours for the routine PCR to 16 hours for the FilmArray. Twenty-six patients could have been removed from isolation 29 hours sooner, 3.6 antibiotic days could have been saved and in five patients additional imaging testing (including colonoscopies) could have been prevented. CONCLUSION: The theoretical implementation of the BioFire FilmArray GI panel in patients with clinical suspicion of gastroenteritis resulted in a significant better patient management.

Characterization of a renal tubular epithelial cell line which secretes the autologous target antigen of autoimmune experimental interstitial nephritis.

Proximal tubular epithelial cells from mice which develop autoimmune interstitial nephritis were found to express the nephritogenic target antigen, 3M-1. Anti-3M-1 mAbs (alpha 3M-1-Ab) were used to positively select for 3M-1-secreting tubular epithelium and, after stabilization in culture, this new cell line (MCT) was examined for the production of several moieties important to either immune interactions or to the development of extracellular matrix. Alkaline phosphatase-staining MCT cells also express epithelial growth factor receptors with a Kd of 0.87 nM and an epithelial growth factor receptor constant (Ro) of 2.1 X 10(4) receptors/cell. MCT culture supernatants contain greater amounts of laminin, and types IV and V procollagens compared to types I and III procollagens, and growing MCT cells on type I collagen matrix causes them to preferentially secrete even more type IV and V procollagen. The 30,000-Mr 3M-1 antigen could be immunoprecipitated from biosynthetically labeled MCT cell supernatants with alpha 3M-1-Ab. An identical-sized moiety was isolated by immunoaffinity chromatography from collagenase-solubilized mouse kidney tubular basement membranes. The 3M-1 antigen can be found on the MCT cell surface by radioimmunoassay, or deposited in a linear array in the extracellular matrix surrounding the MCT cells in culture by immunofluorescence. Mature messenger RNA species for both class I and class II major histocompatibility complex (MHC) molecules were detected by Northern hybridization, and their corresponding cell surface gene products were detected by cytofluorography of MCT cells stained with haplotype-specific antibodies. Both the cell surface 3M-1 and the small amounts of detected class II MHC molecules appear to be biologically functional, as MCT cells can support the proliferation of 3M-1-specific, class II MHC-restricted helper T cells in culture. These findings suggest that MCT cells provide all the necessary biological parameters for interfacing both as the target of a nephritogenic immune response, and as a potential source for new extracellular matrix which develops as a fibrogenic response to interstitial nephritis.

Making the case for cardiovascular screening in Irish males: detection of abdominal aortic aneurysms, and assessment of cardiovascular risk factors.

INTRODUCTION: AAA screening programmes have proven to be beneficial and cost effective worldwide for males greater than 65 years of age, with 4.9% males of 65-75 years of age having an un-diagnosed AAA at screening, resulting in a 42% reduction in the risk of rupture in an English population. This study assessed the incidence of AAA and risk factors for atherosclerosis in Irish males of 55-75 years. METHODS: From April 2006 to December 2007, males between the ages of 55 and 75 years, living within the catchment area of Blanchardstown Hospital were invited for AAA screening using duplex ultrasound and cardiovascular risk factor screening. RESULTS: 1.9% (17/904) of the study population had previously un-diagnosed aneurysms detected, with sizes ranging from 3.0 cm to 5.8 cm (0.6% in 55-65 years old (yo) and 4.2% in 65-75 yo, p<0.01). 33% (302/904) of patients had hyperlipidaemia, while 16% of those with a previous diagnosis of hyperlipidaemia, were inadequately controlled on the test date. 31% of patients had a single elevated blood pressure reading, meriting further investigation for possible hypertension. 3% (28/904) of all patients had a raised glucose levels which had not previously been identified and of those who had a previous history of DM, 46% had abnormal glucose levels. 16% of patients (93/573) were morbidly obese (BMI>30) and 64% (292/573) were overweight. CONCLUSION: The incidence of AAAs in 65-75-year-old men is similar to international figures. This study confirms that screening for hyperlipidaemia, hypercholesterolaemia, obesity and hypertension may be worthwhile in all males over 55 years, while AAA screening should be reserved for 65-75-year-old Irish males.

Concurrent colorectal malignancy and abdominal aortic aneurysm: a multicentre experience and review of the literature.

OBJECTIVES: There is lack of consensus regarding concurrent vs. staged approaches, and the prioritisation of staged procedures in cases presenting with colorectal carcinoma (CRC) and abdominal aortic aneurysm (AAA) synchronously. We aim to present our experience, review the literature on this therapeutic dilemma and examine the role of endovascular aortic repair (EVAR). DESIGN, MATERIALS AND METHODS: An observational study of the experience of two centres and a systematic review of the published literature. RESULTS: Twenty-four patients were identified from the prospective databases of two tertiary referral centres between 2001 and 2006. Intervention for both malignancy and aneurysm was performed in 13 patients. In 10 patients, cancer resection was performed initially and was followed by open aneurysm repair (n=3) or EVAR (n=7). Two patients (AAA diameters: 7.0 and 8.0cm) underwent EVAR prior to colonic resection. One patient was selected for synchronous surgery. There were no interval AAA ruptures, graft infection or postoperative mortalities. Literature review identified 269 such cases; of these 101 were treated by combined surgery. In staged surgery, there were nine interval aneurysmal ruptures and one aortic graft infection. CONCLUSIONS: In our experience, staged management can be undertaken, without interval aneurysmal rupture. EVAR has an evolving role in preventing delay in CRC management, in high-risk patients, and during combined intervention.

Reference range of liver corrected T1 values in a population at low risk for fatty liver disease-a UK Biobank sub-study, with an appendix of interesting cases.

PURPOSE: Corrected T1 (cT1) value is a novel MRI-based quantitative metric for assessing a composite of liver inflammation and fibrosis. It has been shown to distinguish between non-alcoholic fatty liver disease (NAFL) and non-alcoholic steatohepatitis. However, these studies were conducted in patients at high risk for liver disease. This study establishes the normal reference range of cT1 values for a large UK population, and assesses interactions of age and gender. METHODS: MR data were acquired on a 1.5 T system as part of the UK Biobank Imaging Enhancement study. Measures for Proton Density Fat Fraction and cT1 were calculated from the MRI data using a multiparametric MRI software application. Data that did not meet quality criteria were excluded from further analysis. Inter and intra-reader variability was estimated in a set of data. A cohort at low risk for NAFL was identified by excluding individuals with BMI ≥ 25 kg/m2 and PDFF ≥ 5%. Of the 2816 participants with data of suitable quality, 1037 (37%) were classified as at low risk. RESULTS: The cT1 values in the low-risk population ranged from 573 to 852 ms with a median of 666 ms and interquartile range from 643 to 694 ms. Iron correction of T1 was necessary in 36.5% of this reference population. Age and gender had minimal effect on cT1 values. CONCLUSION: The majority of cT1 values are tightly clustered in a population at low risk for NAFL, suggesting it has the potential to serve as a new quantitative imaging biomarker for studies of liver health and disease.

Virtual reality simulation in endovascular surgical training.

BACKGROUND: Shortened trainingtimes duetothe European Working Time Directive (EWTD) and increased public scrutiny of surgical competency have led to a move away from the traditional apprenticeship model of training. Virtual reality (VR) simulation is a fascinating innovation allowing surgeons to develop without the need to practice on real patients and it may be a solution to achieve competency within a shortened training period. METHOD: A Medline search was performed to identify studies and commentaries on the use of VR simulators in endovascular training. FINDINGS: Three studies on carotid stenting and four on peripheral vascular angioplasty demonstrate that simulator training is a valid, feasible and acceptable training tool. One randomised study reports that these skills learned on simulators are transferable to the operating room. CONCLUSION: VR simulators have a role in competency based, structured training of vascular interventionalists and should improve patient safety.

Utility and cost evaluation of multiparametric magnetic resonance imaging for the assessment of non-alcoholic fatty liver disease.

BACKGROUND: Validated diagnostic tools that are accurate, cost effective and acceptable to patients are required for disease stratification and monitoring in NAFLD. AIMS: To investigate the performance and cost of multiparametric MRI alongside existing biomarkers in the assessment of NAFLD. METHODS: Adult patients undergoing standard of care liver biopsy for NAFLD were prospectively recruited at two UK liver centres and underwent multiparametric MRI, blood sampling and transient elastography withing 2 weeks of liver biopsy. Non-invasive markers were compared to histology as the gold standard. RESULTS: Data were obtained in 50 patients and 6 healthy volunteers. Corrected T1 (cT1) correlated with NAFLD activity score (ρ = 0.514, P < .001). cT1, enhanced liver fibrosis (ELF) test and liver stiffness differentiated patients with simple steatosis and NASH with AUROC (95% CI) of 0.69 (0.50-0.88), 0.87 (0.77-0.79) and 0.82 (0.70-0.94) respectively and healthy volunteers from patients with AUROC (95% CI) of 0.93 (0.86-1.00), 0.81 (0.69-0.92) and 0.89 (0.77-1.00) respectively. For the risk stratification of NAFLD, multiparametric MRI could save £150,218 per 1000 patients compared to biopsy. Multiparametric MRI did not discriminate between individual histological fibrosis stages in this population (P = .068). CONCLUSIONS: Multiparametric MRI accurately identified patients with steatosis, stratifies those with NASH or simple steatosis and reliably excludes clinically significant liver disease with superior negative predictive value (83.3%) to liver stiffness (42.9%) and ELF (57.1%). For the risk stratification of NAFLD, multiparametric MRI was cost effective and, combined with transient elastography, had the lowest cost per correct diagnosis.

Effector mechanisms in organ-specific autoimmunity. I. Characterization of a CD8+ T cell line that mediates murine interstitial nephritis.

To further investigate mechanisms of cell-mediated tissue destruction in an organ-specific autoimmune disease, we have established and characterized a nephritogenic CD8+ T cell line. This target antigen-specific effector T cell line, M52, was derived from bulk populations of CD8+ T cells isolated from susceptible animals immunized to produce anti-tubular basement membrane (alpha TBM) disease. Our studies show that M52 retains the phenotypic and functional characteristics of nephritogenic T cells induced in vivo. M52 mediates antigen-specific delayed-type hypersensitivity (DTH) responses to the target antigen 3M-1, it is cytotoxic to 3M-1-expressing renal tubular epithelial cells in vitro, and it adoptively transfers interstitial nephritis to naive syngeneic recipients. Clonal analysis of these nephritogenic CD8+ T cells reveals distinct functional phenotypes within the M52 cell line. We have isolated a cytotoxic CD8+ clone, M52.26, which is not DTH-reactive to 3M-1, and multiple DTH-reactive clones which mediate less efficient cytotoxicity to 3M-1-expressing target cells. Cytofluorographic analysis of four randomly selected clones reveals alpha beta T cell receptor expression. Further characterization of these functionally distinct CD8+ T cell clones will help to define their respective roles in mediating tubular epithelial cell injury and the inflammatory lesion of autoimmune interstitial nephritis.

Inhibition of murine nephritogenic effector T cells by a clone-specific suppressor factor.

We have used a murine model of organ-specific autoimmunity to characterize therapeutic modalities capable of down-regulating the cellular limb of the autoimmune response. Murine interstitial nephritis is an autoimmune disease mediated by tubular antigen-specific CD8+ nephritogenic effector T cells which are delayed-type hypersensitivity (DTH) reactive and cytotoxic to renal epithelial cells. Previous studies have demonstrated that disease can be suppressed with experimentally induced populations of T cells (Ts1 and Ts2 cells) obtained after injection of tubular antigen-coupled splenocytes into syngeneic mice. As the target of Ts2 is the CD8+ effector T cell, we have evaluated its effects on nephritogenic effector T cell clones isolated from diseased animals. Our studies demonstrate that soluble proteins expressed by Ts2 cells (TsF2) specifically abrogate the DTH, cytotoxic, and nephritogenic potential of M52 cells, although T cell receptor and IL-2 receptor expression are unchanged in these unresponsive M52 clones. TsF2-induced inhibition is dependent on new mRNA and protein synthesis. In a cytotoxic clone, M52.26, exposure to TsF2 induces expression of TGF-beta 1 which is, in turn, required for inhibition of cytotoxicity and nephritogenicity. Our studies are consistent with TGF-beta 1 behaving, at least in some T cells, as a nonspecific final effector of clone-specific suppression.

Tubular antigen-binding proteins repress transcription of type IV collagen in the autoimmune target epithelium of experimental interstitial nephritis.

We have been studying immune interactions with somatic cells using a tubular antigen-binding protein (ThF) secreted by helper T lymphocytes harvested from mice that have an autoimmune form of interstitial nephritis called anti-tubular basement membrane disease. This ThF, although characterized originally because of its ability to induce effector T cells, additionally recognizes the nephritogenic 3M-1 antigen expressed by its target renal tubular epithelium. We believe these proteins, in general, may modulate directly some homeostatic functions in organ-derived cells, and now report that our ThF represses specifically the cellular transcription and secretion of basement membrane type IV collagen in tubular epithelium. These in vitro findings of reduced levels of mRNA encoding type IV collagen correlate well with in situ hybridization studies performed on kidneys expressing early autoimmune lesions, and predict a progressive drop in the expression of type IV collagen in the interstitium. Such a novel and unexpected repression of transcription of type IV collagen might easily impart or facilitate permanent change in the infrastructure of kidney architecture during autoimmune injury and, perhaps, contributes to the process of tubular atrophy attendant to prolonged renal inflammation.

Prostaglandin E1 inhibits effector T cell induction and tissue damage in experimental murine interstitial nephritis.

Immunosuppressive effects of E-series prostaglandins have been demonstrated in many in vitro assays of immune responsiveness as well as in autoimmune diseases. To explore the mechanisms underlying prostaglandin E1 (PGE1)-associated immunosuppression in autoimmunity, we treated SJL mice immunized to produce immune-mediated interstitial nephritis with PGE1, PGF2 alpha, or vehicle alone. Mice receiving PGE1 treatment do not develop interstitial nephritis, nor do they display delayed-type hypersensitivity (DTH) to the immunizing renal tubular antigen preparation. The observed immunosuppression is critically dependent on PGE1 administration during the period of effector T cell induction. We therefore investigated the effect of PGE1 on the in vitro induction of DTH effector T cells reactive to renal tubular antigens (SRTA). PGE1 inhibits effector T cell induction in a dose-dependent, reversible manner, but has no inhibitory effect on fully differentiated DTH effector cells or SRTA-reactive cell lines. The PGE1 effect is indirect and mediated via nonspecific suppressor lymphokines. This suppression can be overcome by recombinant interleukin 1 (IL-1), which suggests a mechanism related to either diminished IL-1 secretion or target cell sensitivity to IL-1.