The measurements were performed as described before [16] Briefly

The measurements were performed as described before [16]. Briefly, each patient exhaled FK506 concentration against the fixed expiratory resistance of 16 cm H2O, which resulted in a constant flow of 50 ml/s. A plateau of NO concentration in the exhaled air at the selected exhalation rate was automatically selected by the computer software according to the American Thoracic Society recommendations. The measurements were repeated three times and the mean value expressed as fraction of expired NO (FeNO) was used for analysis. Flow cytometry analysis.  Samples of EDTA anticoagulated venous blood for flow cytometry and cytokine analyses were collected before (T0), 6 h (T6) and 24 h (T24) after allergen challenge. Flow cytometry

analysis was performed on the whole-blood samples using combinations of the following labelled monoclonal antibodies anti-CD14 FITC or anti-CD14 PE, anti-CD16 FITC or anti-CD16 PE-Cy5 and anti-CCR4 PE (all from BD PharMingen, Erembodegen, Belgium) as described before [6]. Labelled, isotype-matched BYL719 antibodies were used as negative controls. After

30 min of incubation at room temperature, erythrocytes were lysed using FACS Lysing Solution (BD PharMingen). The remaining white cells were analysed using FACSCalibur cytometer (BD Immunocytometry Systems, San Jose, CA, USA) as described before [6]. Individual PBM subsets were given names according to the nomenclature proposed by Ziegler-Heitbrock et al. [7]. Immune assays.  Serum concentration of total (tIgE) and specific anti-Dp IgE PDK4 (sIgE) were evaluated using UniCap (Phadia, Uppsala, Sweden). Plasma concentrations of CCL2, CX3CL1 and CCL17 were evaluated using Quantikine ELISA kits (R&D Diagnostics, Minneapolis, MN, USA). Statistical analysis.  The results are expressed as mean with 95% confidence interval (95%CI). Statistical analysis was performed using anova test. Post hoc analysis was performed using Student’s t-test. A probability value of P < 0.05

was taken to indicate statistical significance. Linear correlation by Pearson was used to estimate correlations between studied parameters. Allergen challenge resulted in the development of significant bronchoconstriction in 22 [responders (Rs)] of 34 Dp-APs. Those 22 patients reported both rhinitis and asthma symptoms. In 12 Dp-APs, no asthmatic response could be demonstrated [non-responders (NRs)]. Those patients had never reported asthma symptoms before the study. The baseline clinical and immunologic characteristics of the studied patients are presented in Table 1. There was no difference in age and sex distribution between Rs, NRs and HCs. All Dp-APs had comparable levels of serum tIgE, baseline lung function results and FeNO. The greatest mean eosinophil count was seen in Rs (415 cells/mm3; 95%CI 295–534 cells/mm3) being significantly greater than in NRs (214 cells/mm3; 95%CI 143–321 cells/mm3; P = 0.

6B, do not always correlate well with the levels of Egr2 in norma

6B, do not always correlate well with the levels of Egr2 in normal thymocytes; notably, in population A, where Egr2 expression is lowest, there are substantial effects on Socs1 expression in Egr2f/fCD4Cre mice. We suggest that the regulation of Socs1 by Egr2 is biologically significant, as events previously documented as lying downstream of Socs1 signaling during selection were also affected in Egr2-deficient thymocytes. Egr2-deficient CD4+CD8lo cells were unable to correctly upregulate Bcl2 expression as would normally occur following resumption of cytokine

signaling 30, and this was linked to lowered levels of pStat5 and a reduced ability to survive in IL-7-supplemented medium. We note that survival might be further compromised by the loss of a small population of high-level expressors of IL-7R in Egr2-deficient CD4+CD8lo subsets. BVD-523 Regulation of Socs1 might also provide an explanation for the increase in numbers of CD8SP thymocytes in Egr2-Tg animals, as this fits well with the observations that in the absence of Socs1, CD8SP T-cell differentiation

is enhanced 33. It would be of great interest to determine whether gain of Socs1 is able to rescue this aspect of the Egr2-Tg phenotype. PARP inhibitor We and others have shown that following TCR ligation, both the MAPK and calcineurin signaling pathways are required for induction of Egr2

15, 22. The convergence of these pathways on Egr2 suggests it may lie at a crucial control point in the selection process. Previously, it has been suggested that the expression levels and activity of Egr proteins combine to modulate positive selection following TCR ligation 24. Where the signal is strong, as in the highest affinity TCR interactions with peptide-MHC, Egr2 and its relatives Egr1 and Egr3 are induced at high levels and are not the rate-limiting step in the selection process. However, where the TCR is weak enough for a thymocyte to be on the boundary between positive selection and death by neglect, increased amounts of Egr proteins permit positive selection to occur, and decreased amounts cause the cell to fail selection. Our data suggest PFKL an extension of this model whereby titration of the levels of Egr2 by TCR signal strength could perhaps modulate the cytokine-mediated survival signal by regulating the level of Socs1, thus fine-tuning the process of positive selection. Egr2-Tg mice were made by microinjection into oocytes of Sfi1-linearised pVAhCD2 plasmid 40 containing LoxP-flanked DsRed and Egr2 cDNA. Details of construct are available upon request. Other strains used have been previously published as follows: CD4Cre 27; Egr2f/f28 MHC-deficient mice 41, 42, Rag2−/−43, Rag1−/−44, TCR-β F5 45, TCR-β HY 46 and TCR-β OTII 47.

As the common clinical features of XLP are FIM, EBV-associated HL

As the common clinical features of XLP are FIM, EBV-associated HLH and lymphoproliferative disorder [2, 3], we completed SH2D1A and XIAP gene sequencing in the patients with one or more of these symptoms in this study. Most XLP patients appear healthy prior to contracting EBV [16]. However, following infection, patients often develop T and B cell lymphoproliferation and secondary HLH [16, 17]. Using gene sequencing, we diagnosed five patients with XLP of the 21 male patients in our study with FIM, EBV-associated HLH or persistent EBV

viremia. The overall clinical phenotypes of the affected persons matched those previously reported. All of the five patients had symptoms of HLH and four tested positive for EBV-DNA. This finding indicated that EBV infection triggers HLH in patients with SH2D1A or XIAP deficiency. Although Patient 2 was EBV-DNA negative, we still consider HLH as triggered

GDC-973 by EBV infection based on the elevated atypical lymphocyte counts. Previous study reported that about 13 XLP patients showed hypogammaglobulinemia [18]. In our study, 1 patient with SH2D1A deficiency had lower IgG, IgA and IgM levels, especially IgG. The results indicate that the patient had hypogammaglobulinemia. All four patients evaluated for immunological function showed a low CD4/CD8 ratio, which may be associated with EBV infection. selleck kinase inhibitor In patients with XLP, disease onset is usually Astemizole at 2–5 years of age and is often triggered by EBV infection [16, 19]. Among the five patients in the study, the youngest one was only 1 month old at time of onset. It is different with the western world, maybe due to early encountering of the EBV infection. Although there is no precise epidemiological data of EBV infection, the age of onset is thought to vary widely, with developed countries having

higher ages at primary infection, most likely due to better hygienic conditions and other socioeconomic and demographic factors including household size and population density [20]. The result indicates that patients with SH2D1A or XIAP deficiency can show XLP associated symptoms at a very young age. Prior reports indicate that the prognosis for XLP is poor, with 70% of patients dying before the age of 10 and mortality nearing 96% for those with a history of EBV infection [2, 4, 5]. In our study, three patients had rapid disease progression and died. Only one patient received HSCT and is well. The prognosis observed in our study is therefore similar to previous studies. In summary, we report the clinical and genetic features of five Chinese patients with SH2D1A/XIAP deficiency in this study. For patients with severe EBV-associated HLH, our results indicate the need to consider the possibility of XLP. This work was supported by the National Natural Science Foundation of China (81172877, 81000260) and Shanghai Rising-Star Program (11QA1400700). All authors declare no conflict of interest.

Ultimately, further studies of this population may help us unders

Ultimately, further studies of this population may help us understand and improve the efficacy of immunotherapies that influence IL-2 signaling. The IL-2 receptor alpha chain learn more (CD25) has been used as a marker for Treg cells (CD4+CD25HIFOXP3+) as well as activated T cells [2]. However, analysis of CD4+ cells using two different monoclonal antibodies to CD25 clearly revealed a population of resting FOXP3− human CD4+ T cells that expressed intermediate levels of CD25 [25]. We found that these

two commercially available anti-human CD25 antibodies revealed a significant proportion of CD4+FOXP3− T cells expressed intermediate levels of CD25 (Supporting Information Fig. 1A). We subsequently used clone 4E3 for the remainder of this study and found that CD25INT CD4+ T cells were found in all individuals studied, comprising 35–65% of all CD4+ T cells in normal donors. Representative FACS plots from four individuals are shown in Fig. 1A. To show that this

new antibody recognized functional CD25, CD4+ T cells from fresh PBMCs were stimulated with various concentrations of rhIL-2 and then evaluated for upregulation of intra-cellular pSTAT5, as pSTAT5 is Selleck FDA approved Drug Library downstream of IL-2 signaling (Fig. 1B). Cells expressing higher levels of CD25 responded to lower concentrations of IL-2, while cells expressing little or no CD25 required higher concentrations of rhIL-2. When preincubated with an anti-CD25 blocking antibody that does not interfere

with binding of the 4E3 anti-CD25 antibody, the cells expressing intermediate and high levels of CD25 were unable to respond to the lower concentrations of rhIL-2 but did respond to a higher O-methylated flavonoid dose of rhIL-2, presumably through the β and γ chains of the IL-2 receptor (Fig. 1B). Although we found the CD25INTFOXP3− cells mainly among CD4+ T cells, a small proportion of resting CD8+ T cells also expressed CD25 (Fig. 1C). CD25INT CD4+ T cells were interrogated by flow cytometry for expression of markers of naïve and memory cells. The majority of CD25INT cells expressed the memory marker CD95 (Fig. 1D) [26]. This observation was reaffirmed by the expression of the naïve and memory markers CD45RA and CD45RO (Supporting Information Fig. 1B) [27]. In the normal individuals studied, CD25INT T cells comprise the majority (as much as 80%) of memory cells in the CD4+ T-cell compartment (data not shown). We were unable to find a significant relationship between the percent of CD4+ that were CD25INT as a function of age within the cohort of healthy individuals used in this study (data not shown). We next evaluated whether CD95+CD25NEGFOXP3− and CD95+CD25INTFOXP3− CD4+ T cells maintain their respective CD25 phenotype over time.

albicans, by chemokines production such as KC and MIP-2, importan

albicans, by chemokines production such as KC and MIP-2, important for neutrophils influx [37]. Yet, in candidiasis, TLR2 is involved in TNF-α, PR-171 ic50 MIP-2 [45], IL-12, IFN-γ [46] and IL-10 production [47]. In relation to paracoccidioidomycosis, our data showing preferential involvement

of TLR4 in cytokines production are not in agreement with some studies showing that IL-10 production by dendritic cells or monocytes/neutrophils in response to Pb involves a preferential fungus recognition by TLR2 and dectin-1 instead of TLR4 [48, 49]. The possible explanation for these differences might be related for differences in experimental protocols such as evaluation periods and the blockade or not of receptors. In paracoccidioidomycosis, as in other infections, IL-10 production in response to Pb has been considered as an escape mechanism from host defence. High levels of this cytokine are detected in serum and culture supernatants of patients [50–52], and patients’ monocytes spontaneously release high levels of this cytokine in vitro [53]. In experimental model of the mycosis, higher levels of IL-10 were released by susceptible mice when compared to those of resistant mice [54]. In our laboratory, this cytokine has been demonstrated to inhibit Pb AZD9668 in vivo killing by IFN-γ-activated and TNF-α-activated human monocytes and neutrophils [36, 55]. However, we cannot discard the possible beneficial role of IL-10, controlling excessive inflammatory response induced by pro-inflammatory

cytokines. In a recent study, less virulent strain of Pb was shown to be recognized by TLR2 and dectin-1 with consequent balanced production of TNF-α and IL-10. On the other hand, more virulent strain induced only TNF-α production. Thus, less virulent strain, by IL-10 production, induced a more controlled response, beneficial for the host [49]. Regarding IL-8, studies in our laboratory have demonstrated that this cytokine is involved in an anti-apoptotic effect of Pb on neutrophils, resulting in a delay on cells death, ADP ribosylation factor a process that could allow the fungus to survive intracellularly [56].

In addition, some studies showed that delayed neutrophil apoptosis induced by IL-8 involves signalling by TLR4 [57]. In summary, our data suggest that Pb18 uses TLR4 to gain access to human neutrophils. However, this process does not result in an increase in killing mechanisms by these cells. On the other hand, it is involved in IL-8 and IL-10 production by human neutrophils in response to activator cytokines and/or Pb. Considering that IL-10 and IL-8 are preferentially involved in escape mechanisms of Pb from neutrophil functions, our study points to the idea that Pb interaction with TLR4 on human neutrophils could be considered as a pathogenicity mechanism of this fungus, which would use host receptors of innate immunity to infect cells and to guarantee its own multiplication. We thank Valéria Alves da Silva for helpful assistance in flow cytometry assays. Jossimara Polentini and Dra.

For this reason, methods of abrogating the activity of Treg cells

For this reason, methods of abrogating the activity of Treg cells might be critical for the successful immunotherapeutic treatment of cancer. Studies showed that Treg and Th17

cells co-existed in the microenvironment of different types of tumour, and the development of Th17 cells was described to be linked to that of Treg in a reciprocal fashion; however, information on human bladder cancer Th17/Treg development and differentiation is limited. Our data revealed that Th17 cells were correlated inversely with Treg cells and correlated positively with IFN-γ+ CD4+ T cells in the same tumour microenvironment. It has shown that recombinant IL-2 is a promising agent for the activation of immune response against tumour learn more and plays a central role in balancing Treg cells and IL-17+ T cells in multiple diseases. Kryczek et al. reported that IL-2 regulated Selleck Antiinfection Compound Library the balance between tumour Treg and Th17 cells by stimulating the differentiation of Treg and inhibiting that of Th17 cells [35]. However, Leveque et al. revealed that under some stimulated conditions, IL-2 rapidly converted epithelial ovarian cancer (EOC) Treg into Th17 cells, down-regulated

FoxP3 expression, and lost their suppressive capacity [17]. Due to the above conflicting data, we sought to determine whether IL-2 would also play a role in balancing Treg cells and IL-17+ T cells in bladder cancers. Our results indicated that tumour-infiltrating Treg cells cultured in the presence of the autologous irradiated CD3– fraction and IL-2 could be converted into Th17 cells, which might be involved in the mechanism that instillations of IL-2 into the urinary bladder is effective in the treatment of superficial bladder cancer. In conclusion, the present data suggest that Th17 cells, together with Treg cells, might contribute to the immunopathogenesis of bladder cancer, and inhibition of Th17 cell development might be a novel immune evasion mechanism. We further identified Carnitine palmitoyltransferase II that IL-2 played a role

in balancing Treg cells and IL-17+ T cells by converting bladder cancer Treg into Th17 cells, our results encouraged a deep in vivo exploration of its effects on in situ immune responses. Further studies are still needed to identify the mechanisms of underlying regulation and dynamic interaction among Th17 cells and Treg and Th1 cells in human pathological conditions such as bladder cancer. The authors have no financial conflict of interest. This study was supported by Heilongjiang Province Science Foundation for Youths (project number: QC2009C05), China Postdoctoral Science Foundation, Innovation of science and technology of Harbin youth (project number: 2008RFQXS008) and Foundation of Heilongjiang Educational Committee (project number: 11531160).

hmpdacc org/reference_genomes php) and the assembled and annotate

hmpdacc.org/reference_genomes.php) and the assembled and annotated genomic sequences of this bacterium have been submitted to the GenBank/EMBL/DDBJ selleck compound database (http://www.ncbi.nlm.nih.gov/genome?Db=genome&Cmd=ShowDetailView&TermToSearch=7229; accession number AEVO01000000, and consists of sequences AEVO01000001-AEVO01000169, submitted (31-JAN-2011) by Genome Sequencing Center, Washington University School of Medicine). Based on blast analysis and inspection of the annotation of the draft sequence, it is indicated that there is a lack of the genes for CA in this bacterium. However, the sequence data whole genome shotgun draft generated by illumina reads that it consists of 169 contigs with gaps. Therefore,

we speculate that, as in S. thermophilum, the requirement for CO2 in S. hippei YIT 12066T is due to a CA deficiency. To the best of our knowledge, this is the first report of the isolation of a strictly CO2-requiring bacterium from human GI microbiota. The CO2 concentrations click here required for the growth of S. hippei in the human intestinal tract may be achieved by the metabolic activities of other microbiota. Alternatively, the growth of S. hippei may be supported by bicarbonate secreted into the GI tract from the pancreas (19). The loss of the carbonic anhydrase gene in S. hippei may have occurred as a result of its adapting to its niche, the GI tract, which is rich in CO2/bicarbonate, although it is also possible that the ancestor

of this bacterium did not retain the corresponding gene from the beginning.

No potential conflicts of interest were disclosed. “
“Various studies have shown that dietary glutamine can modify the course of an immune response, through altering the release of cytokines. Nutritional supplementation of glutamine may therefore be of advantage to patients, particularly those with compromised immunity. Given that polymorphisms in cytokine genes can also affect cytokine levels, we have undertaken a study to identify whether there was a differential Meloxicam effect of glutamine supplementation in the context of different IL-2 -330 (T/G) and TNF-α -308 (A/G) genotypes. Overall, there was no significant impact of glutamine supplementation on IL2 release. However, analysing low, medium and high expressors independently, there was an effect of high glutamine levels on cytokine release from the low and medium expressors. Likewise, there was no effect of glutamine supplementation on the TNF-α release, although a tendency to lower cytokine release at high levels of glutamine. Irrespective of the glutamine concentrations, there was no difference in IL2 release between the IL2 -330 genotypes; there was an effect of the TNF-α genotypes, with the AG and GG genotypes showing greater cytokine release than from the AA genotype. The nutritional status is a very important criterion of assessment for patients’ immunocompetence. In certain situations, patients require the reasonable substitution of different dietary components.

For detection of Stat5, CD69+ thymocytes from Egr2f/f and Egr2f/f

For detection of Stat5, CD69+ thymocytes from Egr2f/f and Egr2f/f CD4Cre littermates were purified to 99% purity on MACS columns (Miltenyi Biotech) using Strepatividin-conjugated beads. In total, 0.5×106 thymocytes were stimulated in RPMI-1640, 10% FBS with or without IL-7

(6 ng/mL) for the times indicated. Total cell extract was analysed by Western blot using anti-pStat5 (pY694) and anti-Stat5 (BD transduction laboratories). To assay death in Sorafenib thymocytes, thymocytes were cultured on anti-CD3-coated plates, on uncoated plates, or in the presence of 200 ng/mL dexamethasone (Sigma). Apoptotic and dead cells were visualised with AnnexinV (Nexins Research or BD Biosciences) and DAPI (Sigma) staining, respectively. For IL-7 survival assays, CD69+ thymocytes from Egr2f/f and Egr2f/fCD4Cre mice were purified

on MACS columns (Miltenyi Biotech), stained with CD4 and CD8 fluorescent-conjugated antibodies, and sorted on a Moflo, to obtain CD4+CD8lo populations to 99.9% purity. CD4+CD8lo thymocytes were cultured in 96-well plates with 6 ng/mL IL-7 (R&D Systems) for the indicated times. Cells were harvested and overall cell recovery was determined by counting in a haemocytometer. A proportion of cells were then stained for CD4 and CD8; at the 72 h PLX-4720 concentration timepoint, all cells remained CD4+CD8lo and had not differentiated further (Supporting Information Fig. 4). Statistical significance was calculated using a two-tailed student’s t-test where p values are shown. This work

was supported by Cancer Research UK and RVX-208 the Institute of Cancer Research. The authors thank Fredrik Wallberg, Derek Davies, Demelza Bird, Mathew Sargent and Vladimir Grigoriev for technical assistance, and Patrick Costello and Richard Treisman for helpful discussions. Conflict of interest: The authors declare no financial or commercial conflict of interest. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. “
“The economic consequences of bovine diarrhea are serious. Few long-term epidemiological data are available concerning the causative pathogens of bovine diarrhea in Japan. From 2002 to 2011, surveillance of enteric pathogens was performed in cows of various breed and age from 302 farms in which diarrhea had occurred in Yamagata Prefecture, Japan. Differences between dairy and beef cows in the number of cases of diarrhea and rates of infection by Salmonella spp. and Eimeria spp. were found. Clinical symptoms (duration of epidemic, hematochezia and complications) caused by bovine rotavirus infection were milder than those caused by bovine coronavirus infection.

Data were collected and analyzed Results: Ninety three patients

Data were collected and analyzed. Results: Ninety three patients were involved in this study. Data show that male : female = 46:47, age 52 ± 11, median of dialysis length 29 (7–149) months,

Kt/V 1.4 ± 0.8, average adipose tissue content was 13.01 ± 7.02 kg (23.75 ± 10.93 %), BMI 20.86 ± 3.45, median of hs-CRP 2.623 (0.177–44.139), MI score 6 ± 2. These data showed that the nutritional status measured by adipose, BMI and were still in normal Selleck GS1101 range. Although Indonesian has lower BMI, they had higher percentage of adipose tissue. MIS revealed low score, accordance to hs-CRP result that also showed lower than other studies in Kaukasian and Black people. Conclusions: This study shows that hemodialysis patients in Bandung Indonesia have normal adipose tissue content, lower inflammation status, and low MI score. Key words: Adipose tissue, inflammation, MIS, hemodialysis. 245 COMPARISON OF DIALYSIS PATIENTS’ AND NEPHROLOGIST’S PERCEPTION OF SURVIVAL IN A RURAL SETTING N AUNG, S

MAY Tamworth Base Hospital, New South Wales, Australia Aim: To compare the difference between patients’ perception of their expected survival on dialysis and their treating nephrologist’s expected outcome. Background: Patients with End-Stage Renal Failure Ferrostatin-1 on dialysis are often unaware about their possible survival and this is rarely clearly discussed. Methods: Questionnaire is prepared to collect information from both patients and nephrologists about perception of

survival. We randomly select 15 patients from both in-patients and out-patients settings. Results: Patient’s median age is 64 years old (7 female, 8 male). 2 out 15 identify themselves as Indigenous and the rest are Caucasian. 60% of patients think they will survive more than 10 years but nephrologists think only 13% will. Those patients, who answered lower survival expectation, mostly had the Advanced Care Directive in place (53%). Two thirds of patient answered that a kidney transplant will prolong their survival. Nearly (14/15) would choose quality over quantity of life and their median quality of life is 7 (score from 0 to 10). Nephrologists’ however reason for low survival in 53% was due to cardiac complication and they gave high survival score in patients they assessed as eligible for kidney transplant (60%). Conclusions: There is a significant difference between the patients’ expectation of survival and their treating nephrologists’ expectation. This is an area that needs further exploration. 246 ETHICAL CONSIDERATIONS IN THE TREATMENT OF NON-ADHERENT HAEMODIALYSIS PATIENTS: BALANCING THE ETHICAL PRINCIPLES OF AUTONOMY AND JUSTICE C CORNEY1, S WINCH2 , A KARK1 1Royal Brisbane & Women’s Hospital, Brisbane, Queensland; 2The University of Queensland, Brisbane, Queensland, Australia Non-adherent haemodialysis patients present a challenge both medically and ethically. In-centre haemodialysis is an expensive treatment modality dependent on limited spaces.

The mechanisms by which IL-7 maintains T-cell survival, and there

The mechanisms by which IL-7 maintains T-cell survival, and therefore regulate cellular fitness, have been the subject of numerous studies. Many of these have focused on the transcriptional control of key regulators of apoptosis such as anti-apoptotic factors Bcl2 and Mcl1. Evidence from knockout mice illustrates the importance played by the balance in expression of Bcl2 family members. The defects in thymopoeisis in mice lacking IL-7 or IL-7Rα learn more can be substantially rescued by over-expression of Bcl2 12, 13, or by compound deficiency with pro-apoptotic molecules such as Bax 14 or Bim 15. In vitro, it has long been

recognized that IL-7 stimulation of mutant T-cell lines or primary T cells up-regulates Bcl2 12, 13, 16–18, as well as Mcl1 19. Conversely, there have been other reports suggesting that Bcl2 expression is reduced in the absence of IL-7 signalling 3, 20–22. However, this is not observed in in vitro cultured T cells where particular care was taken to isolate viable cells 23. Therefore, find protocol although IL-7 can transcriptionally regulate Bcl2 expression, it remains unclear whether this accounts for the full range of IL-7 activity in vivo. While the identity of signals that regulate T-cell survival

are known, it remains unclear how such survival signals determine homeostatic fitness in order to regulate T-cell homeostasis in vivo. Are survival signals digital, permitting cell survival when intact and resulting in cell death in their absence, or do T cells indeed exhibit varying degrees of fitness depending on their current exposure to such survival signals? In this study, we report evidence for different mechanisms of IL-7 regulated T-cell survival evoked at different levels of IL-7 signalling. To examine T-cell survival in the absence of IL-7 signalling, we used a mouse model in which class I-restricted F5 TCR transgenic mice conditionally express IL-7Rα using the tetracycline regulatory system (F5 TreIL-7R rtTAhuCD2Il7r−/−, F5 TetIL-7R hereon, see Materials and Methods) 24. Induction of IL-7Rα expression, by feeding mice doxycycline (dox) throughout

life (F5 TetIL-7RON), overcomes the block in thymic development that normally occurs in Il7r−/− F5 mice and allows the generation of a normal peripheral compartment of Oxymatrine F5 T cells. In contrast to the high levels of IL-7Rα found in the thymus, peripheral T cells from dox-fed F5 TetIL-7R mice express much lower levels of IL-7Rα that are not functional in vivo 24. Nevertheless, we have previously shown that withdrawal of dox food from F5 TetIL-7R mice for three days (F5 TetIL-7ROFF) is sufficient to guarantee complete loss of residual IL-7Rα expression (referred to as IL-7R– F5 T cells hereon). Importantly, surface IL-7Rα protein is undetectable on IL-7R– F5 T cells and cells fail to phosphorylate STAT5 in response to IL-7 stimulation in vitro 2.