Phenotypical and functional alterations of CD8 regulatory T cells in primary biliary cirrhosis.

The mechanisms that lead to loss of tolerance in autoimmune disease have remained both elusive and diverse, including both genetic predisposition and generic dysregulation of critical mononuclear cell subsets. In primary biliary cirrhosis (PBC), patients exhibit a multilineage response to the E2 component of pyruvate dehydrogenase involving antibody as well as autoreactive CD4 and CD8 responses. Recent data from murine models of PBC have suggested that a critical mechanism of biliary destruction is mediated by liver-infiltrating CD8 cells. Further, the number of autoreactive liver-infiltrating CD4 and CD8 cells is significantly higher in liver than blood in patients with PBC. Based on this data, we have studied the frequencies and phenotypic characterization of both CD4 and CD8 regulatory T cell components in both patients with PBC and age-sex matched controls. Our data is striking and indicate that CD8 Treg populations from PBC patients, but not controls, have significant phenotypic alterations, including increased expression of CD127 and reduced CD39. Furthermore, in vitro induction of CD8 Tregs by incubation with IL10 is significantly reduced in PBC patients. Importantly, the frequencies of circulating CD4+CD25+ and CD8+ and CD28- T cell subpopulations are not significantly different between patients and controls. In conclusion, these data identify the CD8 Treg subset as a regulatory T cell subpopulation altered in patients with PBC.

Advancements on phenotypic and functional characterization of non-antigen-specific CD8+CD28- regulatory T cells.

Among the different regulatory T lymphocyte (Treg) subpopulations, non-antigen-specific CD8+CD28- Treg (CD8+CD28- Treg) have been characterized for being involved in the pathogenesis of autoimmune diseases and cancer. A better phenotypic and functional characterization of this regulatory T-cell subset could help in identifying modulators of their activity with therapeutic finalities. The results of the present work show that Foxp3, a transcriptional marker of natural CD4+CD25+ Treg, is not expressed by CD8+CD28- Treg, thus indicating different origin and pathways of function for the latter with respect to the former regulatory cell type. Moreover, the results underline that the glucocorticoid induced TNF receptor is involved in generation processes but not in suppressor function of CD8+CD28- Treg. Phenotypic analyses demonstrate that, during their commitment from circulating nonregulatory CD8+CD28- T lymphocytes to Treg (an interleukin-10-dependent process), these cells downmodulate the IL7-receptor, thus differentiating them from long-lived, memory CD8+ T lymphocytes. Interestingly, CD8+CD28- Treg have been found to be resistant to the inhibitory effects of methylprednisolone, one of the most frequently administered corticosteroid drug used in therapy for immunosuppressive purposes.

Endocrine regulation of suppressor lymphocytes: role of the glucocorticoid-induced TNF-like receptor.

Mechanisms responsible for peripheral immune tolerance are currently under investigation in several laboratories, in order to define the role of immune homeostasis in physiological processes and pathologic conditions, such as autoimmunity and cancer. In this context, recent studies attributed a relevant role to the glucocorticoid-induced TNFR-related gene (GITR). GITR is expressed at high levels on CD4(+)CD25(+). T regulatory (Treg) cells, but only at low levels on resting responder T lymphocytes, and is upregulated after activation. GITR triggering induces both pro- and anti-apoptotic effects through different intracellular pathways, abrogates the suppressive activity of Treg cells, and co-stimulates responder T cells. These data hint that GITR triggering overstimulates the immune system. Indeed, in vivo studies demonstrated that GITR stimulation may both induce autoimmune diseases and strengthen anti-virus and anti-tumor immune responses. Therefore, the GITR-GITRL system appears crucial in regulating immunity. Currently, the majority of studies about GITR's role on regulatory cells are focused on CD4(+)CD25(+) Treg cells, while very little is known about the importance of this molecule in other Treg subtypes. We have recently characterized a subpopulation of CD8+ T suppressor lymphocytes able to inhibit both T cell proliferation and cytotoxicity. Preliminary data show that GITR is expressed on such CD8+ T suppressor cells and that its activation by a specific antibody inhibits generation, but not function, of these cells. These early results suggest the importance of GITR in human T suppressor lymphocytes other than CD4(+)CD25(+) Treg cells.

Nonantigen specific CD8+ T suppressor lymphocytes originate from CD8+CD28- T cells and inhibit both T-cell proliferation and CTL function.

Nonantigen specific CD8+ suppressor T lymphocytes (CD8+ Ts) inhibit T-cell proliferation of antigen-specific T lymphocytes. The impossibility to generate in vitro these cells has been correlated with the appearance of relapses in patients affected by autoimmune diseases, suggesting the involvement of these cells in immune regulation. This study was aimed to identify circulating precursors and to characterize the phenotype and mechanism of action of CD8+ Ts. We found that CD8+ Ts can be generated in vitro from CD8+CD28- T lymphocytes, but not from CD8+CD28+ T cells. A key role in their generation is played by monocytes that secrete interleukin-10 (IL-10) after granulocyte macrophage-colony-stimulating factor (GM-CSF) stimulation. Cell-to-cell direct interaction between CD8+CD28- T cells and monocytes does not play a role in the generation of CD8+ Ts. CD8+ Ts have a CD45RA+, CD27-, CCR7-, IL-10Ralpha+ phenotype and a TCR Vbeta chain repertoire overlapping that of autologous circulating CD8+ T cells. This phenotype is typical of T lymphocytes previously expanded due to antigen stimulation. Their suppressive effect on T-cell proliferation targets both antigen presenting cells, such as dendritic cells, and antigen-specific T lymphocytes, and is mediated by IL-10. CD8+ Ts suppress also the antigen-specific cytotoxic activity of CTL decreasing the expression of HLA class I molecules on target cells through IL-10 secretion. These findings can be helpful for the better understanding of immune regulatory circuits and for the definition of new pathogenic aspects in autoimmunity and tumor immunology.

Apoptotic DNA binds to HLA class II molecules inhibiting antigen presentation and participating in the development of anti-inflammatory functional behavior of phagocytic macrophages.

Resident macrophages are mainly responsible for the clearance of apoptotic cells from tissue by phagocytosis. Phagocytosis of apoptotic cells is not accompanied by activation of inflammatory mechanisms, unlike what happens when necrotic phenomena occur. We analyzed the effect of phagocytosis of apoptotic bodies on macrophage cell functions. After phagocytosis of apoptotic cells macrophages were unable to present an exogenous antigen to autologous antigen-specific T-cell lines. The inhibition was mediated by different mechanisms including binding of apoptotic DNA to human leukocyte antigen (HLA) class II molecules of macrophages, decreased expression of co-stimulatory molecules and increased secretion of tumor growth factor beta (TGFbeta). When dendritic cells were cultured with macrophages phagocytosing apoptotic cells, or with their supernatant, impaired dendritic cell antigen presenting activity and reduced tumor necrosis factor alpha (TNFalpha) secretion were found. Our results suggest that: (1) the phagocytosis of apoptotic bodies inhibits macrophage antigen presentation; (2) such inhibition is mediated by the binding of apoptotic DNA to macrophage HLA class II molecules as well as by the activation of biological mechanisms that induce an anti-inflammatory functional behavior in macrophages; and (3) macrophages phagocytosing apoptotic cells inhibit antigen presentation of neighboring dendritic cells via TGFbeta secretion. These events are likely related to the preservation of healthy tissues from the onset of inflammation.

Soluble CD14 subtype presepsin (sCD14-ST) and lipopolysaccharide binding protein (LBP) in neonatal sepsis: new clinical and analytical perspectives for two old biomarkers.

Several biochemical markers have been proposed over the past years to manage critically ill newborns with acute inflammation and sepsis. The state of the art in diagnosing and monitoring neonatal sepsis, severe sepsis and septic shock consists of the measurement of plasma C-reactive protein (CRP) and procalcitonin (PCT) at the onset and in the course of the disease. CRP and PCT in combination are clinically significant in diagnosing and monitoring septic newborns; however, CRP and PCT have a very limited value for risk stratification and in predicting outcome. The availability of commercial methods for the automated measurement of the soluble CD14 subtype presepsin (sCD14-ST) and lipopolysaccharide binding protein (LBP) represent a challenge for the evaluation in clinical practice of reliable markers of neonatal sepsis, specifically for the very early diagnosis, the classification into class of severity, and the prediction of complications and death.

Urine neutrophil gelatinase-associated lipocalin (uNGAL) and netrin-1: are they effectively improving the clinical management of sepsis-induced acute kidney injury (AKI)?

Neutrophil gelatinase-associated lipocalin (NGAL) and Netrin-1 have been proposed over the past years as emergent biomarkers for the early and accurate diagnosis and monitoring of acute kidney injury (AKI). During the early phases of AKI, a rapid and massive up-regulation of NGAL mRNA takes place in the thick ascending limb of Henle's loop and in the collecting ducts, and therefore, changes in urinary NGAL (uNGAL) excretion seem to be more specific than plasma NGAL in assessing early kidney injury. The availability of a new automated immunoassay for measuring uNGAL facilitates its introduction in the clinical routine, especially in an emergency setting. However, in critically ill newborns AKI often develops during sepsis, which in turn induces an up-regulation of NGAL mRNA in neutrophils. To improve the effectiveness of therapeutic treatment in septic newborns with AKI, there is the need to accurately distinguish NGAL molecular forms originating within the distal nephron from those originating from neutrophils. This concise review summarizes properties and perspectives of uNGAL and Netrin-1 for their appropriate clinical utilization.

Combined use of urinary neutrophil gelatinase-associated lipocalin (uNGAL) and albumin as markers of early cardiac damage in primary hypertension.

BACKGROUND: Neutrophil Gelatinase-Associated Lipocalin (NGAL) is an early and specific marker of acute kidney dysfunction. Recent evidences suggest that NGAL may also be involved in chronic vascular remodeling during the development of atherosclerosis. Albuminuria, a powerful predictor of cardiovascular events, is thought to reflect widespread subclinical vascular abnormalities. We investigated the relationship between urinary NGAL (uNGAL), albuminuria and left ventricular mass (LVM) in patients with primary hypertension. METHODS: A total of 120 untreated, non diabetic patients with primary hypertension (mean age 47 ± 9 years) were studied. uNGAL was measured by a chemiluminescent microparticle method, optimized on a fully automated analytical platform (ARCHITECT, Abbott Diagnostics Inc, Rome, IT). Albuminuria was measured by immunonephelometry on an Immage Immunochemistry System (Beckman Coulter, Inc., Fullerton, California, USA) and expressed as albumin/creatinine ratio (ACR). LVM was assessed by echocardiography and indexed to body surface area (LVM/BSA). RESULTS: No significant correlation was found between uNGAL and ACR; however, both variables were directly related to clinic systolic blood pressure (rho=0.241, p=0.0085 and rho=0.248, p=0.0068 respectively), left ventricular relative wall thickness (rho=0.251, p=0.0156 and rho=0.263, p=0.0013 respectively), and LVM/BSA (rho=0.285, p=0.0062 and rho=0.213, p=0.0410 respectively). The uNGAL and ACR simultaneous increase above their respective median values was associated with higher LVM/BSA values (p=0.0109) and with a higher prevalence of left ventricular hypertrophy (LVH) (p=0.0017). Furthermore, logistic regression analysis showed that the risk of presenting LVH increased more than 4-fold when uNGAL and ACR were both above the median value, even after adjustment for age, gender and blood pressure values. CONCLUSIONS: The simultaneous increase in uNGAL and ACR excretion is significantly associated with the increase of LVM in low risk patients with primary hypertension. This association is clinically significant for the early assessment of cardiac damage in hypertension.

Acute kidney injury in critically ill infants: the role of urine Neutrophil Gelatinase-Associated Lipocalin (NGAL).

Acute kidney injury (AKI) has emerged as an important health problem in the intensive care units, especially among infants delivered prematurely. Recent efforts to define and characterize AKI have led to studies of early AKI detection and will ultimately contribute to improvements in AKI outcomes. The discovery of biomarkers for AKI that might enable early recognition and clinical intervention to limit renal injury is therefore of intense contemporary interest. Neutrophil gelatinase-associated lipocalin (NGAL) is the most promising among all emerging markers for AKI; specifically, urine NGAL (uNGAL) predicts renal failure much earlier than serum creatinine. The recent availability of an automated immunoassay for measuring uNGAL in the clinical practice permits to introduce the test in emergency, having a turn around time (TAT) closely comparable with that of serum creatinine. On the basis of data reported in the literature, it is reasonable to forecast an increasing clinical use of uNGAL capable to change our approach to the diagnosis and leading to better preventative and therapeutic interventions which will improve outcomes of critically ill infants with acute kidney disease.

CD8+ CD28- T regulatory lymphocytes inhibiting T cell proliferative and cytotoxic functions infiltrate human cancers.

Tumor growth is allowed by its ability to escape immune system surveillance. An important role in determining tumor evasion from immune control might be played by tumor-infiltrating regulatory lymphocytes. This study was aimed at characterizing phenotype and function of CD8+ CD28- T regulatory cells infiltrating human cancer. Lymphocytes infiltrating primitive tumor lesion and/or satellite lymph node from a series of 42 human cancers were phenotypically studied and functionally analyzed by suppressor assays. The unprecedented observation was made that CD8+ CD28- T regulatory lymphocytes are almost constantly present and functional in human tumors, being able to inhibit both T cell proliferation and cytotoxicity. CD4+ CD25+ T regulatory lymphocytes associate with CD8+ CD28- T regulatory cells so that the immunosuppressive activity of tumor-infiltrating regulatory T cell subsets, altogether considered, may become predominant. The infiltration of regulatory T cells seems tumor related, being present in metastatic but not in metastasis-free satellite lymph nodes; it likely depends on both in situ generation (via cytokine production) and recruitment from the periphery (via chemokine secretion). Collectively, these results have pathogenic relevance and implication for immunotherapy of cancer.

Frequency of telomerase-specific CD8+ T lymphocytes in patients with cancer.

Telomerase is considered a universal tumor-associated antigen (TAA) due to its high rate of expression by cancers (approximately 90%), and clinical trials are in progress to test the immunotherapeutical efficacy of antitelomerase immunization in patients with cancer. However, the data concerning frequency and functional activity of telomerase-specific cytotoxic T lymphocytes (CTLs) in patients with cancer are few and conflicting, although their knowledge would be mandatory to predict the efficacy of telomerase-specific immunotherapy in selected patients. We performed this study to analyze frequency and cytolytic function of circulating CD8+ T lymphocytes specific for the p540 telomerase peptide in a series of human leukocyte antigen (HLA)-A2+ cancer patients. The results show that most patients with cancer have circulating telomerase-specific CD8+ T lymphocytes, but a high frequency of telomerase-specific CTLs are present only in a fraction of them. Furthermore, CTL lines able to kill telomerase-positive tumor cells, including autologous cancer cells, can be expanded ex vivo from some, but not all, patients with cancer. In conclusion, the results of the study support the development of clinical protocols using telomerase peptides as an immunizing agent. However, they underline the necessity to study single patients immunologically before undergoing vaccination, to select the patients adequately, and to eventually adapt the immunization schedule to the patient's immunologic status.