Influence of CD4+/CD25+ regulatory T cells on atherogenesis in patients with end-stage kidney disease.

Atherosclerosis, which is influenced by both traditional and nontraditional cardiovascular risk factors and has been characterized as an inflammatory process, is considered to be the main cause of the elevated cardiovascular risk associated with chronic kidney disease. The inflammatory component of atherosclerosis can be separated into an innate immune response involving monocytes and macrophages that respond to the excessive uptake of lipoproteins and an adaptive immune response that involves antigen-specific T cells. Concurrent with the influx of immune cells to the site of atherosclerotic lesion, the role of the adaptive immune response gradually increases. One of those cells are represented by the CD4+/CD25+ Tregs, which play indispensable roles in the maintenance of natural self-tolerance and negative control of pathological, as well as physiological, immune responses. Altered self-antigens such as oxidized LDLs may induce the development of CD4+/CD25+ Tregs with atheroprotective properties. However, atherosclerosis may be promoted by an imbalance between regulatory and pathogenic immunity that may be represented by the low expression of the forkhead box transcription factor (Foxp3) in CD4+/CD25+ Tregs. Such a defect may break immunologic tolerance and alter both specific and bystander immune suppression, leading to exacerbation of plaque development. Patients with end-stage kidney disease (ESKD) display a cellular immune dysfunction and accelerated atherosclerosis. Uremic solutes that accumulate during ESKD may be involved in these processes. In patients with ESKD and especially in those that are chronically hemodialyzed, oxidative stress induced by oxidized LDLs may increase CD4+/CD25+ Treg sensitivity to Fas-mediated apoptosis as a consequence of specific dysregulation of IL-2 expression. This review will focus on the current state of knowledge regarding the influence of CD4+/CD25+ Tregs on atherogenesis in patients with ESKD, and the potential effect of statins on the circulating number and the functional properties of these cells.

Cutting edge: cell autonomous rather than environmental factors control bacterial superantigen-induced T cell anergy in vivo.

Anergic T cells display a marked decrease in their ability to produce IL-2 and to proliferate in the presence of an appropriate antigenic signal. Two nonmutually exclusive classes of models have been proposed to explain the persistence of T cell anergy in vivo. While some reports indicate that anergic T cells have intrinsic defects in signaling pathways or transcriptional activities, other studies suggest that anergy is maintained by environmental "suppressor" factors such as cytokines or Abs. To distinguish between these conflicting hypotheses, we employed the well-characterized bacterial superantigen model system to evaluate in vivo the ability of a trace population of adoptively transferred naive or anergized T cells to proliferate in a naive vs anergic environment upon subsequent challenge. Our data clearly demonstrate that bacterial superantigen-induced T cell anergy is cell autonomous and independent of environmental factors.

Determinants of vaccine immunity in the cohort of human immunodeficiency virus-infected children living in Switzerland.

BACKGROUND: Human immunodeficiency virus (HIV)-infected children are at increased risk of infections caused by vaccine preventable pathogens, and specific immunization recommendations have been issued. METHODS: A prospective national multicenter study assessed how these recommendations are followed in Switzerland and how immunization history correlates with vaccine immunity. RESULTS: Among 87 HIV-infected children (mean age: 11.1 years) followed in the 5 Swiss university hospitals and 1 regional hospital, most (76%) had CD4 T cells >25%, were receiving highly active antiretroviral treatment (79%) and had undetectable viral load (60%). Immunization coverage was lower than in the general population and many lacked serum antibodies to vaccine-preventable pathogens, including measles (54%), varicella (39%), and hepatitis B (65%). The presence of vaccine antibodies correlated most significantly with having an up-to-date immunization history (P<0.05). An up-to-date immunization history was not related to age, immunologic stage, or viremia but to the referral medical center. CONCLUSIONS: All pediatricians in charge of HIV-infected children are urged to identify missing immunizations in this high-risk population.

Clonal acquisition of the Ly49A NK cell receptor is dependent on the trans-acting factor TCF-1.

Families of clonally expressed major histocompatibility complex (MHC) class I-specific receptors provide specificity to and regulate the function of natural killer (NK) cells. One of these receptors, mouse Ly49A, is expressed by 20% of NK cells and inhibits the killing of H-2D(d) but not D(b)-expressing target cells. Here, we show that the trans-acting factor TCF-1 binds to two sites in the Ly49A promoter and regulates its activity. Moreover, we find that TCF-1 determines the size of the Ly49A NK cell subset in vivo in a dosage-dependent manner. We propose that clonal Ly49A acquisition during NK cell development is regulated by TCF-1.

CD28-negative cytolytic effector T cells frequently express NK receptors and are present at variable proportions in circulating lymphocytes from healthy donors and melanoma patients.

In humans, NK receptors are expressed by natural killer cells and some T cells, the latter of which are preferentially alphabetaTCR+ CD8+ cytolytic T lymphocytes (CTL). In this study we analyzed the expression of nine NK receptors (p58.1, p58.2, p70, p140, ILT2, NKRP1A, ZIN176, CD94 and CD94/NKG2A) in PBL from both healthy donors and melanoma patients. The percentages of NK receptor-positive T cells (NKT cells) varied strongly, and this variation was more important between individual patients than between individual healthy donors. In all the individuals, the NKT cells were preferentially CD28-, and a significant correlation was found between the percentage of CD28- T cells and the percentage of NK receptor+ T cells. Based on these data and the known activated phenotype of CD28- T cells, we propose that the CD28- CD8+ T cell pool represents or contains the currently active CTL population, and that the frequent expression of NK receptors reflects regulatory mechanisms modulating the extent of CTL effector function. Preliminary results indicate that some tumor antigen-specific T cells may indeed be CD28- and express NK receptors in vivo.

Dominant human CD8 T cell clonotypes persist simultaneously as memory and effector cells in memory phase.

The adaptive immune system plays a critical role in protection at the time of secondary infection. It does so through the rapid and robust reactivation of memory T cells which are maintained long-term, in a phenotypically heterogeneous state, following their primary encounter with Ag. Although most HLA-A*0201/influenza matrix protein(58-66)-specific CD8 T cells from healthy donors display characteristics typical of memory T cells, through our extensive phenotypic analysis we have further shown that up to 20% of these cells express neither the IL-7 receptor CD127 nor the costimulatory molecule CD28. In contrast to the majority of CD28(pos) cells, granzyme B and perforin were frequently expressed by the CD28(neg) cells, suggesting that they are effector cells. Indeed, these cells were able to kill target cells, in an Ag-specific manner, directly ex vivo. Thus, our findings demonstrate the remarkable long-term persistence in healthy humans of not only influenza-specific memory cells, but also of effector T cells. We further observed that granzyme B expression in influenza-specific CD8 T cells paralleled levels in the total CD8 T cell population, suggestive of Ag-nonspecific bystander activation. Sequencing of TCR alpha- and beta-chains showed that the TCR repertoire specific for this epitope was dominated by one, or a few, T cell clonotype per healthy donor. Moreover, our sequencing analysis revealed, for the first time in humans, that identical clonotypes can coexist as both memory and effector T cells, thereby supporting the principle of multipotent clonotypic differentiation.

Minimal information about T cell assays: the process of reaching the community of T cell immunologists in cancer and beyond.

Many assays to evaluate the nature, breadth, and quality of antigen-specific T cell responses are currently applied in human medicine. In most cases, assay-related protocols are developed on an individual laboratory basis, resulting in a large number of different protocols being applied worldwide. Together with the inherent complexity of cellular assays, this leads to unnecessary limitations in the ability to compare results generated across institutions. Over the past few years a number of critical assay parameters have been identified which influence test performance irrespective of protocol, material, and reagents used. Describing these critical factors as an integral part of any published report will both facilitate the comparison of data generated across institutions and lead to improvements in the assays themselves. To this end, the Minimal Information About T Cell Assays (MIATA) project was initiated. The objective of MIATA is to achieve a broad consensus on which T cell assay parameters should be reported in scientific publications and to propose a mechanism for reporting these in a systematic manner. To add maximum value for the scientific community, a step-wise, open, and field-spanning approach has been taken to achieve technical precision, user-friendliness, adequate incorporation of concerns, and high acceptance among peers. Here, we describe the past, present, and future perspectives of the MIATA project. We suggest that the approach taken can be generically applied to projects in which a broad consensus has to be reached among scientists working in fragmented fields, such as immunology. An additional objective of this undertaking is to engage the broader scientific community to comment on MIATA and to become an active participant in the project.

Can hTERT peptide (540-548) -specific CD8 T cells recognize and kill tumor cells?

This commentary reviews the data on HLA-A2-restricted CD8 T cells specific for peptide (540-548) derived from hTERT (human telomerase reverse transcriptase). Several studies have reported the successful generation of such T cells (1, 2, 3). However, tumor recognition was observed in some, but not all, studies. More data are required to elucidate whether hTERT peptide (540-548) -specific T cells can indeed recognize and destroy tumor cells. It would be highly useful if telomerase would emerge as a universal tumor antigen that can be targeted in the cancer immunotherapy of HLA-A2 positive patients.

Secretory IgA, a major immunoglobulin in most bovine external secretions.

Bovine secretory IgA (SIgA), recently identified in colostrum, was shown to be homologous to human SIgA by immunologic cross-reaction. A quantitative study indicated that bovine SIgA, a minor component of colostrum, is a major immunoglobulin in most other external secretions including saliva, spermatic fluid, lacrimal, nasal and gastrointestinal secretions. SIgA was isolated from saliva. The free form of secretory component was found to be abundant in milk. A normal lactating cow produces about 1.2 g of this protein per day. Two forms of IgA were identified in serum: a normal serum IgA with no secretory antigenic determinant, and a small amount of SIgA. In vitro synthesis of SIgA by the salivary gland was studied by tissue cultures with incorporation of labeled amino acids.

An allele-specific, stochastic gene expression process controls the expression of multiple Ly49 family genes and generates a diverse, MHC-specific NK cell receptor repertoire.

Mouse NK cells express MHC class I-specific inhibitory Ly49 receptors. Since these receptors display distinct ligand specificities and are clonally distributed, their expression generates a diverse NK cell receptor repertoire specific for MHC class I molecules. We have previously found that the Dd (or Dk)-specific Ly49A receptor is usually expressed from a single allele. However, a small fraction of short-term NK cell clones expressed both Ly49A alleles, suggesting that the two Ly49A alleles are independently and randomly expressed. Here we show that the genes for two additional Ly49 receptors (Ly49C and Ly49G2) are also expressed in a (predominantly) mono-allelic fashion. Since single NK cells can co-express multiple Ly49 receptors, we also investigated whether mono-allelic expression from within the tightly linked Ly49 gene cluster is coordinate or independent. Our clonal analysis suggests that the expression of alleles of distinct Ly49 genes is not coordinate. Thus Ly49 alleles are apparently independently and randomly chosen for stable expression, a process that directly restricts the number of Ly49 receptors expressed per single NK cell. We propose that the Ly49 receptor repertoire specific for MHC class I is generated by an allele-specific, stochastic gene expression process that acts on the entire Ly49 gene cluster.

Ex vivo detectable human CD8 T-cell responses to cancer-testis antigens.

Clinical trials have shown that strong tumor antigen-specific CD8 T-cell responses are difficult to induce but can be achieved for T-cells specific for melanoma differentiation antigens, upon repetitive vaccination with stable emulsions prepared with synthetic peptides and incomplete Freund's adjuvant. Here, we show in four melanoma patients that ex vivo detectable T-cells and thus strong T-cell responses can also be induced against the more universal cancer-testis antigens NY-ESO-1 and Mage-A10. Interestingly, all patients had ex vivo detectable T-cell responses against multiple antigens after serial vaccinations with three peptides emulsified in incomplete Freund's adjuvant. Antigen-specific T-cells displayed an activated phenotype and secreted IFNgamma. The robust immune responses provide a solid basis for further development of human T-cell vaccination.

A novel approach to characterize clonality and differentiation of human melanoma-specific T cell responses: spontaneous priming and efficient boosting by vaccination.

Despite major progress in T lymphocyte analysis in melanoma patients, TCR repertoire selection and kinetics in response to tumor Ags remain largely unexplored. In this study, using a novel ex vivo molecular-based approach at the single-cell level, we identified a single, naturally primed T cell clone that dominated the human CD8(+) T cell response to the Melan-A/MART-1 Ag. The dominant clone expressed a high-avidity TCR to cognate tumor Ag, efficiently killed tumor cells, and prevailed in the differentiated effector-memory T lymphocyte compartment. TCR sequencing also revealed that this particular clone arose at least 1 year before vaccination, displayed long-term persistence, and efficient homing to metastases. Remarkably, during concomitant vaccination over 3.5 years, the frequency of the pre-existing clone progressively increased, reaching up to 2.5% of the circulating CD8 pool while its effector functions were enhanced. In parallel, the disease stabilized, but subsequently progressed with loss of Melan-A expression by melanoma cells. Collectively, combined ex vivo analysis of T cell differentiation and clonality revealed for the first time a strong expansion of a tumor Ag-specific human T cell clone, comparable to protective virus-specific T cells. The observed successful boosting by peptide vaccination support further development of immunotherapy by including strategies to overcome immune escape.

Pathogenesis of adult-onset Still's disease: new insights from the juvenile counterpart.

Adult-onset Still's disease (AOSD) is a rare inflammatory disease characterized by the classical triad of daily fever, arthritis, and typical salmon-colored rash. Recent accumulation of knowledge, mostly arising from hereditary autoinflammatory diseases and from the systemic-onset juvenile idiopathic arthritis (sJIA), has given raise to new hypotheses on the pathophysiology of AOSD. In this review, we first discuss on the continuum between AOSD and sJIA. Then, we summarize current hypotheses on the underlying pathogenesis: (1) an infectious hypothesis; (2) an autoinflammatory hypothesis; (3) a lymphohistiocytic hypothesis; and (4) a hyperferritinemic hypothesis. Finally, we present the recent data suggesting that patients with AOSD fall into two distinct subgroups with different courses, one with prominent systemic features and one with chronic arthritis.

Diagnostic immunologique du cancer

Two different types of immunological reaction are of assistance in the diagnosis of cancer: The first is detection of a weak immunological response of the patient toward his own tumor cells. Unfortunately the currently available techniques for the demonstration of humoral or cellular immunological reaction against autologous tumor cells are not reproducible enough to be recommended as routine clinical tests. Secondly, it is possible to use antisera, obtained by immunization of animals with human tumor extracts, for the detection of substances released into the blood by the tumor cells. The two major antigens associated with human cancer that can be measured in the blood by very sensitive immunological methods are the alphafetoprotein (AFP) and the carcinoembryonic antigen (CEA). It is very important for the physician to be fully alive to the usefulness and limitations of such tests in order to interpret them correctly. Clinical situations in which the measurement of AFP and CEA can provide useful information are reviewed.