As shown in Fig 3A, the expression levels of FOXP3 and IFN-γ in

As shown in Fig. 3A, the expression levels of FOXP3 and IFN-γ in expanded E3-Th17 cells were not significantly altered even after culture for 9 days. However, the number of IL-17-producing cells significantly decreased during the culture, from above 60% to approximately 40%. Recent studies have shown that the stable expression of FOXP3 in

naturally occurring Tregs involves epigenetic regulations, including DNA methylation and histone modification 41, 43. Furthermore, these studies demonstrated that human FOXP3 contains several highly conserved demethylation regions that are exclusive for Tregs. Thus, we next investigated whether expanded Th17 cells expressing FOXP3 exhibited FOXP3 DNA demethylation. We designed the human FOXP3 methylation-specific primers based on the Treg-specific demethylated region (TSDR) within the OSI-906 mouse FOXP3 CpG island 43–45, and then compared the FOXP3 methylation levels in expanded Th17 cells, CD4+CD25+ naturally occurring Tregs and OKT3-activated naïve CD4+ T cells. As expected, the TSDR within FOXP3 of CD4+CD25+ Tregs was almost completely demethylated

compared with that of CD4+CD25– T cells (Fig. 3B). In contrast to CD4+CD25+ Tregs, FOXP3 methylation levels of two OKT3-activated naïve T cells were similar to levels in CD4+CD25– T cells (100% methylation), although approximately 15% of these activated cells expressed FOXP3. However, Th17 clones derived from different rounds of expansion displayed partial methylation in GSI-IX manufacturer TSDR within FOXP3, and this decreased significantly with increasing stimulation and expansion cycles. In addition, demethylation

levels of FOXP3 in Th17 clones at different expansion cycles were correlated positively with FOXP3 expression (Fig. 3B). These results indicate that epigenetic modification of FOXP3 occurred in Th17 cells following multiple cycles of in vitro TCR stimulation, resulting in increased Interleukin-3 receptor and stable expression of FOXP3 in expanded Th17 cells. It is well known that TCR–ligand interactions are critical for T-cell lineage commitment, including FOXP3 induction and Treg lineage differentiation 3, 16. Given that Th17 clones differentiate into IFN-γ-producing and FOXP3+ T cells after in vitro expansion, we next investigated whether TCR stimulation is the primary determinant for this process. E1-Th17 clones were expanded in vitro with allogeneic PBMCs in the presence or absence of OKT3 and then evaluated for the IL-17, IFN-γ, and FOXP3 expression. As shown in Fig. 4A, the proportions of IL-17-producing cell populations in Th17 clones were significantly decreased after in vitro expansion, regardless of whether the system included OKT3 or not. Notably, the Th17 clones contained higher percentages of IL-17-producing cells when cultures included both PBMCs and OKT3 than those in the absence of OKT3.

The mammalian target of rapamycin (mTOR) signaling is of central

The mammalian target of rapamycin (mTOR) signaling is of central importance for the integration of environmental signals 1. The mTOR protein is a member of two distinct signaling complexes, mTOR complexes 1 and 2 (mTORC1 and mTORC2), with each complex mediating unique and non-redundant signaling pathways.

mTORC1 is composed of mTOR, which directly interacts with GβL and Raptor, and is sensitive to rapamycin. Conversely, mTORC2 associates with Rictor to form a complex that is insensitive to acute rapamycin treatment 2, 3. T-cell receptor (TCR) engagement activates both mTORC1 and mTORC2, which is dependent on the RasGRP1-Ras-Erk1/2 pathway and is inhibited by diacylglycerol kinases 4–6. Inhibition of mTORC1 by rapamycin induces T-cell anergy Selleckchem KU-60019 and promotes the generation of inducible regulatory T (iTreg) cells 7, 8. In the absence of mTOR, T cells normally upregulate CD25 and CD69, and produce equivalent amounts of IL-2 after TCR stimulation. However, mTOR-deficient T cells exhibit

defective Th1, Th2, and Th17 lineage differentiation, adopting instead the Treg-cell fate 9. Additional evidence indicates that mTORC2 is of central importance in the differentiation of T cells into Th1 and Th2 lineages by regulating Akt and PKC-θ, respectively 10. Interestingly, and contrary to its perceived immunosuppressive properties, treating mice with rapamycin results in the generation of a larger and more effective memory CD8+ Enzalutamide solubility dmso T-cell pool against viral infection and regulates transcriptional programs that determine effector and/or memory cell fates in CD8+ T cells 11, 12. Using rapamycin, it has also been demonstrated that mTOR signaling regulates the trafficking of T cells in vivo by modulating the expression of the chemokine receptor CCR7 13. While it is becoming clear that mTOR signaling is involved in many aspects of T-cell biology, how the mTOR complexes are regulated, and the importance of their regulation in T cells remain poorly understood. The tuberous sclerosis complex (TSC), a heterodimer of TSC1 and TSC2, is

a potent upstream regulator of mTORC1 14. The TSC complex, by virtue of its GAP activity, inactivates Ras homolog enriched in brain (RheB) by MG-132 manufacturer decreasing the GTP bound active form of Rheb, subsequently inhibiting mTORC1 activation 15, 16. Germ-line deletion of TSC1 in mice results in embryonic lethality 17. Deletion of TSC1 in hematopoietic stem cells (HSCs) converts them from a normally quiescent state into a highly proliferative population correlated with increased mitochondrial content and reduced hematopoietic competency 18. In this report, we demonstrate that TSC1 is critical for T-cell survival and the maintenance of a normal peripheral T-cell pool. Its deficiency causes constitutive activation of mTORC1, inhibition of mTORC2 and Akt activity, decreased mitochondrial content, and impaired mitochondrial membrane integrity in T cells.

1E), suggesting a dysregulated expansion of donor TEFF cells in t

1E), suggesting a dysregulated expansion of donor TEFF cells in the absence of TREG cells. In order to examine kinetics of lymphocyte proliferation in TCR-β−/− recipient mice, cycling cells from secondary lymphoid tissues and LP were determined by intracellular Ki-67 expression at different time points during disease progression. Our results show a progressive

increase in frequencies and selleckchem absolute numbers of cycling lymphocytes in colitic mice (Fig. 1F), which was significantly decreased in all lymphoid organs examined, as well as in the LP, upon TREG-cell co-transfer (Fig. 1F and G). More importantly, the reduced absolute numbers of donor TEFF cells in mesLN compared with LP (Fig. 1G) suggests that TREG cells hamper the expansion and accumulation of pathogenic cells in the site of Idasanutlin research buy tissue inflammation. Studies show that a prominent role for Th1, and in particular Th17, polarized immune responses in autoimmunity and IBD-like disorders in humans and in mouse models 44, 45. In particular,

IL-17-secreting T cells are found in lesions of patients with CD 4, 22, 25, and genome-wide association studies of CD and ulcerative colitis patients indicate the importance of Th17-promoting factors, including IL-23, in IBD 46, 47. We then sought to characterize the inflammatory nature of the mucosal inflammation. We observed a significant increase in IFN-γ IL-1β, IL-12 and IL-6 mRNA expression in colons of mice reconstituted with

CD4+CD25− TEFF cells alone, while CD4+CD25+ TREG cell-mediated protection from colitis correlated with higher levels of IL-4 and IL-10 mRNA expression (Fig. 2A). Moreover, we found a marked increase in frequencies and absolute numbers of IFN-γ- and IL-17-producing lymphocytes in secondary lymphoid tissues and LP of colitic mice (Fig. 2B–E), indicating that TREG cells potently Montelukast Sodium suppress the priming and expansion of these cells in protected mice. Interestingly, our results reveal a temporal difference in the emergence of IFN-γ- and IL-17-producing cells. While IFN-γ was highly expressed in the absence of TREG cells in both perLN and mesLN (Fig. 2B), IL-17 secretion was more specific to the intestinal tissue (Fig. 2B and C). This is consistent with previous studies pointing to the mucosa as a privileged site for Th17-cell development due to elevated secretion of specific polarizing mediators such as IL-6 and TGF-β1 25. Moreover, while the frequency of IFN-γ-secreting CD4+ TEFF cells (≈40% of CD4+ T cells) in the inflammatory site remained unchanged during colitis development, the frequency of IL-17+ donor CD4+ TEFF cells steadily dropped from 35% at day 7 to 20% at day 21 (Fig. 2D and E), suggesting a role for different signals in the initial and progressive phases of T-cell-induced colitis in TCR-β−/− mice.

1B and D), implying that as priming with DbPA224 normally stimula

1B and D), implying that as priming with DbPA224 normally stimulates a much broader spectrum of TCRβ than is the case for DbNP366, this diversity could help to ensure the integrity of the response when TCRα is limiting. Interestingly, the DbNP366>DbPA224 this website immunodominance hierarchy recognized for secondary responses to wt influenza A viruses in H2b mice 21 was no longer maintained in A7 transgenics (Fig. 1E–H). Similar to

the primary response (Fig. 1A–D), the DbNPCD8+ sets recovered from the spleen (Fig. 1E and G) and BAL (Fig. 1F and H) of the secondarily infected A7 mice were reduced in magnitude (p<0.05) compared with those from the B6 controls. A possible explanation is that some of the DbNP366-specific TCRβ that pair with this irrelevant Vα chain may not form TCR that can be efficiently recruited after secondary challenge, leading to the A7 DbNPCD8+ and DbPACD8+ recall responses being of comparable magnitude. The next question was whether limiting the available TCRαβ pairs by confining the response to an “irrelevant” TCRα in any way reflects that such “aberrantly selected” TCRαβ use a different

mode of pMHC-I recognition. We made sequential alanine (A) substitutions at different positions within NP366–374 and PA224–233 peptides, excluding the anchor residues (p5, p9 for NP366; p5, p10 for Selleck MAPK inhibitor PA224). These mutant NP366 and PA224 peptides were used to probe CD8+ T-cell responsiveness as determined by IFN-γ production. The recognition profiles of polyclonal DbNPCD8+ and DbPACD8+ T cells obtained from mice primed-and-boosted with influenza viruses (H1N1 then H3N2) were modified by different aa substitutions (Fig. 2A and B). Following infection of A7 mice, p6M and p4E were critical for TCR recognition by DbNPCD8+ T cells (Fig. 2A), whereas p6F and p7R were important for DbPACD8+ T cells (Fig. 2B). These Protirelin profiles were identical to those found previously for B6 mice (Fig. 2) 17, 22. It thus seems that the Vα2-constrained and DbNP366- and DbPA224-specific TCR recognize the same features within the antigenic peptides, raising the question of whether the DbNP366 and DbPA224 epitopes are recognized by the same CDR3β clonotypes in A7 and wt B6

animals. Furthermore, these peptide recognition data suggest that the Vβ-chain may play a dominant role in antigen recognition for both DbNPCD8+ and DbPACD8+ T-cell responses. Alternatively, for the Vα chain to participate in pMHC-I recognition, it might be expected not to have any structural features that would interfere with pMHC-I docking in A7 mice. To determine the clonal composition defined by TCRβ diversity, the DbNP366-specific CD8+ T cells were first analyzed for Vβ usage by staining with a panel of anti-Vβ mAb. In B6 mice, Vβ8.3 consistently accounts for an average of 42.8% 14, 23 of the DbNPCD8+ response, with Vβ4 24 being subdominant (∼13%). This strong Vβ8.3 bias was no longer apparent for the A7 mice (Fig. 3A). However, Vβ4 emerged for DbNP366-specific T cells from spleen (51.4%; range 18.

The ΔiucDΔmhuA strain did not grow in the presence of hemoglobin

The ΔiucDΔmhuA strain did not grow in the presence of hemoglobin as an iron source but could still grow to some extent in the presence of heme (Fig. 7a). This suggests that V. mimicus possesses Bortezomib purchase an additional

receptor which can recognize only heme, but is less effective in utilization of heme than MhuA, although MhuA is sufficient for utilizing hemoglobin. It has been reported that V. cholerae possesses three heme receptor genes, hutA, hutR, and hasR, and that mutation of all three genes is required to make this bacterium incapable of utilizing heme, while its hemoglobin utilization is abolished by the deletion of only the hutA and hutR genes (43). A current objective of our laboratory is to examine whether another heme receptor(s) is present in V. mimicus. Moreover, further studies are needed to elucidate an ABC transporter for the heme moiety in this species. We thank the late Prof. I. Stojiljkovic for providing E. coli H1717 in the FURTA system, Dr. T. Kuroda for providing E. coliβ2155 and a suicide vector pXAC623 as well as for helpful comments on our work, and Dr. S. Busby for providing

E. coli WAM131 and a lac expression vector pAA224. “
“Despite many theoretical incompatibilities between mouse and human selleck kinase inhibitor cells, mice with reconstituted human immune system components contain nearly all human leukocyte populations. Accordingly, several human-tropic pathogens have been investigated in these in vivo models of the human immune system, including viruses such as human immunodeficiency virus (HIV) and Epstein-Barr virus (EBV), as well as bacteria

such as Mycobacterium tuberculosis and Salmonella enterica Typhi. While these studies initially aimed to establish similarities in the pathogenesis of infections between these models and the pathobiology in patients, recent investigations have provided new and interesting functional insights into the protective value of certain immune compartments and altered pathology upon mutant pathogen infections. As more tools and methodologies are developed to make Dichloromethane dehalogenase these models more versatile to study human immune responses in vivo, such improvements build toward small animal models with human immune components, which could predict immune responses to therapies and vaccination in human patients. The complexity of infections and the corresponding elicited immune responses are best investigated in animal models that allow the manipulation of the timing and dose of infection, as well as of the responding immune compartments. Small animal models, such as the mouse, are preferred for these types of investigations due to low costs and ease of handling. However, divergent evolution between these small mammals and humans in the past 65 million years has rendered the immune system the third most different organ system between the two species, after olfaction and reproduction [1].

From our study and others, we can deduce that there are several p

From our study and others, we can deduce that there are several possible mechanisms by which triptolide inhibits airway remodelling in asthma. First, triptolide may inhibit directly airway cell proliferation by anti-proliferative activity against a broad spectrum of mitogens, or by decreasing the transcription and translation of cyclin selleck chemical D1, which consequently arrest the cell cycle progression late in the G1 phase.34 Second, a decrease of the TGF-β1 level is a possible mechanism. We observed a reduction in TGF-β1 expression at both mRNA and protein levels in the lung following triptolide treatment. Finally, triptolide

could modulate the activity of the TGF-β1 signalling pathway. In our study, we observed an elevation of Smad7 expression and suppression of pSmad2/3 by triptolide. Our study indicates that airway remodelling is an irreversible airway hyperplasia process that contributes to airway hyper-responsiveness and irreversible airflow

limitation. Treatment with triptolide or dexamethasone could prevent and inhibit the airway remodelling process in allergic airway diseases, but does not tend to reverse the remodelling. In summary, our study demonstrated that triptolide inhibited asthma airway wall remodelling through mechanisms involving a decrease in the production of TGF-β1 mRNA and TGF-β1 as well as modulation of active TGF-β1 signalling in the NVP-BKM120 molecular weight lung. This small-molecule natural product may prove to be a candidate for the systemic therapy of asthma airway remodelling. However, additional studies exploring the in vitro biological activity of triptolide are needed to support its use as a potential treatment for asthma MTMR9 airway remodelling. The authors have no financial conflicts of interests. “
“Human T cells expressing CD56 are capable of tumour cell lysis following

activation with interleukin-2 but their role in viral immunity has been less well studied. Proportions of CD56+ T cells were found to be highly significantly increased in cytomegalovirus-seropositive (CMV+) compared with seronegative (CMV−) healthy subjects (9·1 ± 1·5% versus 3·7 ± 1·0%; P < 0·0001). Proportions of CD56+ T cells expressing CD28, CD62L, CD127, CD161 and CCR7 were significantly lower in CMV+ than CMV− subjects but those expressing CD4, CD8, CD45RO, CD57, CD58, CD94 and NKG2C were significantly increased (P < 0·05), some having the phenotype of T effector memory cells. Levels of pro-inflammatory cytokines and CD107a were significantly higher in CD56+ T cells from CMV+ than CMV− subjects following stimulation with CMV antigens. This also resulted in higher levels of proliferation in CD56+ T cells from CMV+ than CMV− subjects.

All tested patient sera and IVIG enhanced phagocytosis of the EB

All tested patient sera and IVIG enhanced phagocytosis of the EB in a comparable manner. The presence of complement increased the uptake of beads, and yet this effect did not mask the influence of Eap on phagocytosis (Fig. 3b). As it is well known that Eap binds to cell surfaces, we ensured that EB were phagocytosed rather than attached to the cell surface: using immunofluorescence microscopy on parallel samples, it was demonstrated that in PBMC and granulocytes, EB were exclusively intracellularly located.

This finding contrasts with assays performed with endothelial cells where beads were found both intracellularly as well as on the cell surface (Fig. 4). This study demonstrated that anti-Eap antibodies are detectable in every tested healthy individual as well as in patients suffering selleck chemicals from acute and chronic S. aureus infections. We found that antibody titers were significantly Epigenetics Compound Library ic50 higher in patients

when compared with healthy controls. However, both groups showed a remarkable variability in titers, making it impossible to define a distinct cutoff. Therefore, the anti-Eap antibodies appear not to be suitable as a serological marker for the diagnosis or the prognosis of S. aureus infections. In accordance with our previous findings on eap transcription (Joost et al., 2009), here, we observed that patients with deep infections showed significantly higher anti-Eap titers than patients with superficial infection. Eap is known for its adhesive properties and has often been assigned a role in chronic infections (Lee et al., 2002; Harraghy et al., 2003; Athanasopoulos et al., 2006). We found that patients with long-lasting infections like abscesses or spondylodiscitis exhibited high antibody titers against Eap. Thymidylate synthase These findings imply that the concentration of Eap transcribed

within the infected tissue and the duration of the infection govern the subsequent antibody production. In contrast, the more acute manifestations of S. aureus disease in patients with bacteremia and sepsis were not associated with higher antibody titers than in patients with localized infections. In vitro, Eap has been shown to induce the production of interleukin-6 and tumor necrosis factor-α (Scriba et al., 2008), indicating a possible role of Eap in septic shock. However, the type and duration of antigen presentation is likely to be different in deep-seated tissue infections compared with sepsis; therefore, the contribution of Eap to the cytokine release associated with sepsis and the production of anti-Eap antibodies in the setting of more chronic, tissue-associated S. aureus infection may be seen as two sides of the same coin. To our knowledge, so far, only one other study has investigated antibodies in humans against Eap (also designated as Map) (Dryla et al., 2005a). In contrast to our results, Dryla and colleagues reported no differences between patients and controls.

The level of serum FGF23 increases with developing chronic kidney

The level of serum FGF23 increases with developing chronic kidney disease. However, it is still unclear the effect of hemodialysis (HD) and type of P-binder on regulation of FGF23. We determined the change of serum FGF23 after initiation of HD and compared between calcium bicarbonate (C) and lanthanum carbonate (La) group in FGF23 regulation. Methods: Eighteen patients, introducing hemodialysis from April to September

in 2012, were participated under the informed consent. The participants were randomly divided into two groups, i.e. C and La group. Serum level of FGF23, whole parathyroid hormone (PTH), calcium and phosphate were measured at the initiation of HD and subsequent 3 months. Results: The levels R428 mw of FGF23 increased after introducing HD, although the serum phosphate was managed completely. The level of whole PTH was decreased after the starting HD. There was no significant difference in the serum FGF23 level between C and La group. Urinary P excretion was also different between them. Conclusion: Maintaining

removal of uremic substances by HD and type of P-binder did not influence the FGF23 Selumetinib regulation. Longer observation might be needed to determine the trend of serum FGF23 in patients. HONG YU AH1, KO GANG JEE1, JUNG MI YEON1, CHO YOO SUN1, OH SOO YOUNG1, SEO JAE HEE1, PYO HEUI JUNG1, SUH SANGIL2, KWON YOUNG JOO1 1Department of Internal Medicine, Korea University College of Medicine; 2Department of Radiology, Korea University College of Medicine Introduction: Cinacalcet has been played a role in treatment of secondary hyperparathyroidism (SHPT) refractory to previous medical treatment. However, the method predicting

treatment response of cinacalcet was not established yet. We aimed to investigate whether radiologic P-type ATPase examinations would be helpful to determine the response of cinacalcet treatment. Methods: The research was done with two study populations. First, 26 patients who received dialysis more than 3 months in single center were evaluated the size of parathyroid glands with three different radiologic examinations, which were sonographic measurement for diameter and volume of each gland by 3 dimentional reconstruction by one expert, and computed tomography (CT). After 20 weeks of cinacalcet treatment, predicting value of each radiological examination for the responder group who were defined as patients with PTH Results: Among 26 patients, 17 patients were responders (65.3%). Baseline serum calcium and PTH, and post-treatment ALP and PTH were lower in responder group. The means of diameter in sonography and CT, and gland volume measured by sonography were not significantly different between responder and nonresponder.

However, this housing-associated difference was not present in th

However, this housing-associated difference was not present in the infected mice (Fig. 6). The present study shows that the provision of nesting material, a nest box and a wooden chew block does not alter the immune response to chronic mycobacterial infection, as assessed by the organ

bacterial load, the serum level of IFN-γ, the numbers of different cells populations in the 3-Methyladenine nmr spleen and the activation status of CD4+ T cells (the most relevant cell type on the acquired immune response against mycobacteria). In addition, basic physiological parameters such as body weight gain and body temperature were not altered by the enrichment. To our knowledge, this is the first time that a simple, practical and ethologically relevant environmental enrichment has been evaluated for immunology research during a chronic infection. The results obtained strongly suggest that this type of enrichment can be incorporated in chronic infection studies without affecting the research

results. Even though the aim of the study was to address whether housing enrichment Talazoparib concentration would impact on the immune response to infection, a group of non-infected animals was included as a control for the immunological parameters. The present study shows that even when slight changes in immune cell populations are induced by providing cage enrichments, these do not modulate the course

of infection by M. avium. Previous studies have also described alterations Phosphoprotein phosphatase on the percentage of CD4+ and CD8+ T cells in non-infected mice housed in enriched and super-enriched cages (cages bigger than the regular size and containing various structures) [16]. The activity of T and NK cell has also been shown to be influenced by other environmental conditions, namely the number of male mice housed per cage [15] and the use of super-enriched cages including running-wheels [38]. This brings us to another aspect for discussion: the possibility that enrichment influence stress, a recognized factor that alters response to infection. In previous studies, male mice housed in super-enriched cages showed decreased resistance to the parasite Babesia microti, and this was associated with increased social stress and increased circulating corticosterone levels [39]. On the contrary, increased resistance was observed in Herpes Simplex virus-infected mice housed in cages containing running-wheels [40]. It should be noticed that the majority of studies addressing the effect of housing conditions in the immune system per se, or on the ability of the immune system to fight infecting microorganisms, have essentially evaluated quite extreme situations that differ considerably in the social stress caused to the animals [15, 41], or in the ability to perform physical exercise.

In particular, studies using noninflammatory, cellular antigens s

In particular, studies using noninflammatory, cellular antigens showed that early primary CD8+ T-cell responses can in fact be T-cell help-independent—even in these OTX015 mw noninflammatory conditions. In the absence of

T-cell help during the first 3–4 days, functional effector CD8+ T cells were generated with respect to their ability to produce IFN-γ as well as IL-2, but they were unable to mount productive recall responses [[10, 56]]. Thus, although potent primary CD8+ T-cell responses can be induced in the absence of T-cell help in many viral or bacterial infections, it became clear the generation of proliferation-competent memory CD8+ T cells as well as their long-term maintenance is in many experimental systems dependent on CD4+ T-cell help (Table 2 and 3) [[28, 54, 56]]. Although the phenomenon of poor secondary expansion of “helpless” CD8+ T cells held true for many in vivo experimental systems [[34]], there

are also reports demonstrating that “helpless” CD8+ T cells are not necessarily impaired in their recall proliferation potential [[26, 30, 57]]. The intrinsic molecular program that instructs the recall proliferation defect of unhelped memory CD8+ T cells remains incompletely understood and several mechanistic pathways have been proposed. It was shown that elevated levels of T-bet in “helpless” LCMV-specific CD8+ T cells repress the transcription of IL-7Rα and thereby drive the differentiation of effector memory CD8+ T cells at the expense Selleck Apoptosis Compound Library of central memory CD8+ T cells. Selleckchem Obeticholic Acid Interestingly, deletion of T-bet restores the pool of central memory CD8+ T cells as well as their functional properties [[58]]. In addition, there is evidence that increased levels of TRAIL mRNA found in “helpless” memory CD8+ T cells account for their defective secondary

expansion [[59]]. This finding was challenged by other studies showing that TRAIL deficiency is insufficient to overcome the defective functionality of “helpless” memory CD8+ T cells [[60, 61]], indicating that increased TRAIL expression in “helpless” CD8+ T cells does not fully account for their impaired phenotype and function. As there is no consensus on a strict T-cell help-dependent programming of proliferation-competent memory CD8+ T cells, it is likely that inherent differences in the experimental models account for the different outcomes. Thus, it is important to assess the T-cell help-dependence of (memory) CD8+ T-cell responses and the underlying mechanisms closely linked to the particular experimental system used. Based on the observation that T-cell help is critical for the functionality of memory CD8+ T cells, which are generated in response to many infections or immunizations, the exact timing that is involved in delivering help to CD8+ T cells is still controversial. Currently, there are two different models (programming versus maintenance) discussed.