As depicted in Fig. 8(a), cell–cell contact between CD4+ responder T cells and TGF-β/RA-induced CD8+ Foxp3+/GFP+ T cells is mandatory for the regulatory function of these cells. As a result of the cell–cell contact-dependency of TGF-β/RA-induced Selleck MLN0128 CD8+ Foxp3+/GFP+ T cells and the fact that modulation of antigen-presenting cells (APC) is one of several postulated mechanism of CD4+ regulatory T-cell-mediated suppression we further investigated the role of DCs in a T-cell suppression assay. Therefore, we performed inhibition assays with and without the presence of DCs. Interestingly, the

suppressive activity of TGF-β/RA-induced CD8+ Foxp3+/GFP+ T cells is only detectable in the presence of DCs (Fig. 8b). This finding suggests that TGF-β/RA-induced CD8+ Foxp3+/GFP+ T cells exert their suppressive function by modulating the stimulatory function of DCs. The intestinal immune system is constantly challenged by foreign antigens and commensal bacteria. Therefore, proper control of the intestinal microenvironment is required. One important arm of this regulatory network consists of regulatory T cells. Many researchers have undertaken association studies among patients with IBD to determine whether changes in regulatory T cells can be correlated with disease severity, with a particular focus

on defining the differences between circulating cells and cells from gut tissue. Most of these studies have analysed CD4+ CD25+ Foxp3+ selleck chemicals regulatory T cells, and much less is known about the role of CD8+ regulatory T cells in IBD. Mayer and colleagues suggested that a defect of CD8+ regulatory T cells in the LP may lead to the development of IBD.14,15 These researchers demonstrated that CD8+ T cells isolated from non-inflamed mucosa display suppressive Fenbendazole capabilities; in contrast, LP CD8+ T cells derived from patients with IBD could not suppress immune responses. They conclude that CD8+ T cells with regulatory activity are present in

the LP of normal healthy persons but not in the LP of patients with IBD. In the present study we demonstrated that the peripheral blood of patients with UC contains fewer CD8+ CD25+ Foxp3+ T cells when the disease is active. These findings are in line with those of earlier studies, which demonstrated that the peripheral blood of patients with Crohn’s disease and UC contains fewer CD4+ regulatory T cells during disease flares, and suggest that the severity of disease is inversely correlated with the number of regulatory T cells in the peripheral blood.22–24 Despite our limited understanding of the role of regulatory T cells in the pathogenesis of human IBD, the ability to alter regulatory pathways may be a crucial avenue for achieving long-term remission. Results from animal models suggest that the transfer of regulatory T cells may be beneficial.

The high affinity integrin interaction with its ligands allows for the arrest and adhesion of the leukocyte on the endothelial cell — a process that is necessary for the subsequent transmigration into PLX4032 the targeted tissue. Once leukocytes gain access to the appropriate tissue, they migrate to their particular targets along chemotactic or haptotactic gradients [16]. Finally, at their target site, the retention of leukocytes

in the tissue is tightly controlled and for T cells and DCs, this process is regulated by the lysophospholipid shingosine 1-phosphate (S1P) and by the chemokine receptor CCR7 and its ligands CCL19 and CCL21 [17-20]. On T cells, the differential expression of particular combinations of selectins, chemokine receptors, and integrins on leukocytes is highly regulated and results in a directed trafficking of cellular subsets to particular organs and tissue beds. Naïve T cells, for example, largely express the chemokine receptor CCR7 and the selectin CD62L, which directs them to circulate through the SLOs where they are more likely to have a productive interaction with antigen and antigen-presenting cells [13]. Once activated Crizotinib in vitro by antigen, the activated

effector T cells upregulate the expression of chemokine receptors that correspond and can react to the chemokine ligands produced in inflamed tissues. For CD4+ T cells, the combination of chemokine receptors that are upregulated correlates with the cell-differentiation program upon activation. Thus, CXCR3 and CCR5 are preferentially upregulated on Th1 cells while Th2 cells preferentially express CRTH2, CCR4, and CCR8 [21]. The Th17 subset preferentially expresses CCR6 [22], and Pregnenolone T follicular

helper cells express CXCR5 [23, 24]. Memory T cells can be divided into CCR7+, CD62Lhi central memory T cells that circulate in the SLOs and CCR7−, CD62Llo effector memory T cells, which traffic to peripheral tissues [25]. Interestingly, among T effector memory cells there appears to be a difference in the expression of P and E selectins by CD4 and CD8 cells, resulting in further differences of localization and migration of these lymphocyte subsets within the memory population [26]. The site where antigen is encountered by the naïve cell also affects the expression of chemokine receptors and integrins, “imprinting” them to return to particular tissue beds. This process has been best characterized for the gut and skin but also may occur in the CNS and lung [27]. In the mesenteric lymph nodes and GALT, for example, DC-produced retinoic acid induces the expression of CCR9 and the integrin α4β7 on effector memory T cells. As the ligands for CCR9 and α4β7 (CCL25 and MAdCAM-1, respectively) are mainly expressed on endothelial cells in the venules of the small intestine, these effector memory T cells then specifically home to the gut [28, 29].

Although the number of known HLA alleles increases

from year to year, click here now reaching almost 2000 alleles at HLA-B (Table 2), only part of this polymorphism is detected in individual populations because of typing and statistical limitations (i.e. variable levels of typing resolution, and generally low sample sizes). However, most human populations exhibit a high level of HLA diversity. Table 3 summarizes data on the variation in the number of classical HLA alleles according to two independent studies. For most loci (except genes coding for the α chains of class II molecules, which are less polymorphic), between 10 and 30 alleles are observed per population, the largest number being observed at HLA-B (mean ∼ 30–32). With the exception of the DPB1 locus, and populations that underwent rapid genetic drift (see below), HLA

alleles generally exhibit low to medium frequencies, and many of them are very rare (and hence, rarely detected). Actually, 60–70% of known classical HLA alleles have only been reported up to three times,44,45 suggesting that new allele variants are being generated on a regular and ongoing basis. For most HLA loci, allele frequency distributions are usually even (except in some cases), and Ribonucleotide reductase populations see more achieve very high heterozygosity levels. This is reflected by the elevated mean heterozygosity values found

at each locus (Table 3), the highest value being observed for HLA-B (∼ 91%). Actually, with the exception of HLA-DPB1, heterozygosity levels are often higher than expected for populations undergoing neutral evolution (i.e. only submitted to stochastic factors linked to the history of human populations, like genetic drift and migration),46–50 which is consistent with the action of natural selection favouring heterozygosis. This hypothesis is also confirmed at the molecular level: at all classical HLA loci except DPB1 (and, to a lesser extent, DQB1), most alleles observed within populations are distantly related from a molecular point of view, with often more than 20 diverging nucleotides among their DNA sequences at exon 2 (and exon 3, for HLA class I).51 These HLA loci may therefore be experiencing asymmetric balancing selection where heterozygous genotypes having molecularly distant alleles would have a higher fitness than heterozygous genotypes exhibiting closely related alleles.51 By contrast, classical selective neutrality tests (e.g. Ewens–Watterson tests) performed at the DPB1 locus generally indicate a neutral model of evolution.

Additionally CD4+ Treg have been isolated from humans and correlated with protection against autoimmune disease 7, 9–11. Naturally occurring CD4+CD25+FOXP3+ Treg have received much attention, demonstrating regulatory function in humans and rodents 1. Their growth and

development is dependent on FOXP3 expression, IL-2 and TGF-β, but they do not produce buy Aloxistatin IL-2 and reside in a hyporesponsive state. CD4+CD25+FOXP3+ Treg can mediate regulation in a cell contact dependent manner and involve cell surface molecules such CTLA-4 and TGF-β 12, 13. In addition to naturally occurring populations, CD4+ Treg can also be induced. For example, IL-10-producing Tr1 cells and TGF-β-producing Th3 cells can be induced to mediate bystander suppression 7, 14. We have previously characterized a distinct subset of naturally-induced CD4+ Treg that target autoaggressive Vβ8.2+ T-cell responses for down-regulation and protect against autoimmune disease, such as EAE and collagen-induced arthritis 6, 15–17. Treg cell lines

and clones were MLN0128 chemical structure successfully generated, which displayed reactivity towards a peptide (B5) derived from the conserved framework 3 region of the TCR Vβ8.2 chain 6, 16, 17. We used these T-cell lines and clones throughout this study and will be referred to as CD4+ Treg in this manuscript 3. We have shown that these Treg arise spontaneously during the recovery phase of myelin basic protein (MBP)-induced EAE in the H-2u mouse 6 and during arthritis

in the H-2q mouse 16. Furthermore, clinical disease is exacerbated and recovery hindered after the depletion or inactivation of TCR peptide-reactive CD4+ Treg 17. Additionally, we have shown CD4+ Treg function in unison with CD8αα+ TCRαβ+ Treg, in a mechanism that results in the cytotoxic killing of disease-mediating Vβ8.2+ T cells 3, 15, 18, 19. Upon activation, CD4+ Treg provide “help” for the CD8αα+ TCRαβ+ Treg effector response to proceed 3. However, little is known regarding how CD4+ Treg are naturally Farnesyltransferase primed to initiate immunosuppression mechanisms. Here we delineate a novel mechanism involved in the priming of an antigen-specific CD4+ Treg population. During active EAE an increased frequency of peripheral TCRVβ8.2+ T cells have been detected to be undergoing apoptotic cell death 20, 21. Professional APC, such as DC and macrophages, are adept at ingesting apoptotic cells for both clearance purposes and the presentation of antigen material to the adaptive immune system 22. It has been demonstrated that following ingestion of apoptotic B cells, DC can process and present antigens derived from the dying cell’s B-cell receptor via MHC class II pathway to prime CD4+ T cells 23. We have recently described a novel mechanism by which immature BM-derived DC can ingest apoptotic Vβ8.2+ T cells, process antigen through the endosomal pathway and present a Vβ8.

The field is confused by a lack of standardization in definitions and methodology, and emphasis should be on investigating the underlying mechanisms behind peripheral blood flow changes with local cold exposure. “
“Please cite this paper as: Taylor MS, Francis M, Qian X, Solodushko V. Dynamic Ca2+ signal modalities in the vascular endothelium. Microcirculation 19: 423–429, 2012. The endothelium is vital to normal vasoregulation. Although acute vasodilation associated with broad endothelial Ca2+ elevation is well known, the control and targeting of Ca2+-dependent signals in the endothelium are poorly understood. Recent studies have revealed localized GDC0199 IP3-motivated

Ca2+ events occurring basally along the intima that may provide the fundamental basis for various endothelial influences. Here, we provide an overview of dynamic endothelial Ca2+ signals and discuss the potential role of these signals in constant endothelial control of arterial tone and the titration of functional responses in vivo. In particular, we focus on the

functional architecture contributing to the properties and ultimate impact of these signals, check details and explore new avenues in evaluating their prevalence and specific modalities in intact tissue. Finally, we discuss spatial and temporal effector recruitment through modification of these inherent signals. It is suggested that endothelial Ca2+ signaling is a continuum in which the specific framework of store-release components and cellular targets along the endothelium allows for differential modes of Ca2+ signal expansion and distinctive profiles of effector recruitment. The precise composition and distribution of these inherent components may underlie dynamic endothelial control and specialized functions of different vascular beds. “
“Please cite this paper as: Clark, Jensen, Kluger, Morelock, Hanidu, Qi, Tatake, Pober (2011). MEK5 is Activated by Shear Stress, Activates ERK5 and Induces KLF4 to Modulate TNF Responses

in Human Dermal Microvascular Endothelial Cells. Microcirculation18(2), 102–117. Objective:  ECs lining arteries respond to LSS by suppressing pro-inflammatory changes, in part through the activation of MEK5, ERK5 Niclosamide and induction of KLF4. We examined if this anti-inflammatory pathway operates in human ECs lining microvessels, the principal site of inflammatory responses. Methods:  We used immunofluorescence microscopy of human skin to assess ERK5 activation and KLF4 expression in HDMECs in situ. We applied LSS to or overexpressed MEK5/CA in cultured HDMECs and assessed gene expression by microarrays and qRT-PCR and protein expression by Western blotting. We assessed effects of MEK5/CA on TNF responses using qRT-PCR, FACS and measurements of HDMEC monolayer electrical resistance. We used siRNA knockdown to assess the role of ERK5 and KLF4 in these responses. Results:  ERK5 phosphorylation and KLF4 expression is observed in HDMECs in situ. LSS activates ERK5 and induces KLF4 in cultured HDMECs.

To the best of our knowledge, characterization

of the cross-clade neutralizing antibodies in HIV-1-infected Chinese sera was rarely reported previously. Zhang and colleagues reported serological studies on a cohort of infected homosexual men in Beijing, China, and identified plasmas with cross-clade neutralization and showed that CD4bs-specific antibodies were critical components in these samples. However, 2G12- or PG9-like antibodies were not identified [34]. In this study, we screened 80 serum samples derived from HIV-1-positive individuals against a minipanel of HIV-1 pseudoviruses, including two laboratory-adapted isolates and three primary isolates, and 8 CNsera were identified. Gp120-directed AZD0530 mouse antibodies were prevalent,

while MPER-directed AZD2281 order antibodies were rare, suggesting that the cross-clade neutralizing activities of the CNsera were mainly contributed by the antibodies targeting gp120. In order to characterize the nature of the neutralization and to investigate the epitope specificity of the serum antibodies, we examined antibodies specific for the MPER, the V3 loop, the CD4bs and glycan moiety on gp120. 2F5- and 4E10-like antibodies were only detected in Serum 15 but unlike 2F5 and 4E10, these serum antibodies did not have broad neutralization activities. They accounted for about 80% Clomifene neutralizing activity of Serum 15 against CNE40 but failed

to neutralize JRFL, consistent with a previous study that some sera containing 4E10-like antibody failed to neutralize 4E10-sensitive isolates [25]. The observation demonstrated that broadly neutralizing 2F5- and 4E10-like antibodies rarely developed in the Chinese individuals who were infected with mostly non-B subtypes, consistent with the observations in North America and Western Europe [35] where B subtype dominates. A plausible mechanistic explanation has been proposed for its rarity [35]. V3 peptides derived from the sequences of three primary HIV-1 isolates were synthesized. JV3 derived from a clade B isolate JRFL carries a GPGR sequence at the tip of the PND, 55V3 derived from a CRF01_AE isolate CNE55 with a GPGQ sequence at the tip of the PND and 6V3 derived from a clade B’ isolate CNE6 expresses a rare GLGR at the tip of the PND. Binding data suggested that V3 peptide-reactive antibodies were widely present in these sera, but most of the V3-directed antibodies in CNsera were not the major contributor to the cross-clade neutralization activity although some of the V3 antibodies could effectively neutralize sensitive isolates such as CNE40 and HXB2.

Marco Colonna, learn more University of Washington, Saint Luis, MO, USA). Anti-CD300e, anti-KIR2DL5 and anti-TREM-1 mAb used in functional assays were purified from ascites by affinity chromatography on protein G-sepharose columns (GE Healthcare Bio-Sciences AB) and treated with polymixin B agarose (Detoxi-Gel™ AffinityPack™ pre-packed columns, Pierce, Rockford, IL, USA) for inactivation of any traces of LPS or LPS-related

molecules. A neutralizing TNF-α reagent (Enbrel, Immunex, Thousand Oaks, CA, USA) was used for blocking experiments (10 μg/mL). Flat-bottom 24-, 48- or 96-well plates (Greiner Bio-One GmbH) were coated with 10 μg/mL of anti-CD300e or isotype-matched controls mAb for 3–4 h at 37°C. Freshly isolated cells were added to the wells and cultured for 24 or 48 h at 37°C in 5% CO2 atmosphere. To test the effects of priming on CD300e signaling, freshly isolated monocytes were stimulated for selleck products 1 h at 37°C in 5% CO2 atmosphere with sub-optimal concentrations (10, 1 and 0.1 ng/mL) of ultra pure Escherichia coli LPS (InvivoGen, San Diego, CA, USA) and incubated in the presence of plate-coated anti-CD300e

or isotype-matched control mAb for 24 h at 37°C in 5% CO2 atmosphere. Cells were incubated on ice in 15% human serum to block Fc receptors in a round bottom 96-well culture plate (Corning, Corning, NY, USA). Subsequently cells were incubated with either anti-CD300e (UP-H1 or UP-H2) or appropriate isotype control Ab, followed by staining with a PE-conjugated rabbit anti-mouse Ab (DakoCytomation Denmark A/S, Glostrup, Denmark) and analyzed by FACS. The following murine mAb were used: PE-conjugated anti-CD3,

anti-CD14 (BD Biosciences and GmbH, Friesoythe, Germany), nearly anti-CD25 (ImmunoTools GmbH, Friesoythe, Germany), anti-CD40, anti-CD54, anti-CD83 or anti-CD86 (all from BD Pharmingen, San Diego, CA, USA); FITC-conjugated anti-CD3 (BD Biosciences), anti-CD4, anti-CD45R (ImmunoTools GmbH) and PE-Cy5-conjugated anti-CD11c (BD Pharmingen). For each staining, the appropriate PE-, FITC- or PE-Cy5-conjugated isotype controls were included (ImmunoTools GmbH) and cells were analyzed on either FACScan, FACSCalibur or FACSCanto (Becton Dickinson, San Jose, CA, USA) flow cytometers. For each staining, we collected at least 10 000 events by gating on viable cells. Data analysis was performed using the FlowJo software (Three Star, Ashland, OR, USA). To compare the staining intensity of different samples in some cases, we calculated the ratios between the geometric MFI of samples and isotype-matched controls (MFIsample/MFIisotype control). The number of cells (y-axis) is normalized for the different overlaid samples and represented as “% of Max” by using the FlowJo software. For measurement of intracellular calcium by flow cytometry, freshly isolated monocytes in complete RPMI (1×107/mL) were loaded with 1 mM indo-1 AM (Sigma Aldrich) for 30 min at 37°C.

Antibodies against the following molecules coupled to the indicated fluorochromes were purchased from BD Pharmingen (San Diego, CA, USA): CD4-FITC, CD8-PE, CD3-biotin, CD25-biotin, CD44-FITC, CD62L-biotin, CD69 PECy7. Biotin-conjugated-anti-CD24, APC-Cy7-conjugated-anti-CD8, anti-CD3ε and anti-CD28 were purchased from Biolegend (San Diego, CA, USA). A700-conjugated-anti-CD4 and PercP-conjugated-anti-CD8 Carfilzomib in vitro were purchased from eBioscience (San Diego, CA, USA). The determination of

cell survival in fresh or cultured thymocytes was conducted by staining with Annexin V (BD Biosciences) and propidium iodide (Sigma-Aldrich, St Louis, MO, USA) after surface staining for CD4 and CD8. The anti-cylindromatosis 1 (E-4), (E-10), anti-p65/RelA (A), anti-p50/NF-kB1(C-19), anti-IKK2 (T-20) and anti-JNK (D-2) antibodies were obtained from Santa Cruz Biotechnology. The anti-pJNK

(9251) antibody was obtained from Cell Signaling. The anti-actin mouse monoclonal antibody was purchased from MP Biomedical (Solon, OH, USA). Single-cell suspensions were obtained from thymus, spleen and lymph nodes by the dissociation of isolated tissues through a 60-μm mesh. Red blood cells were excluded by Gey’s lysis solution and debris was removed by cell strainer. Cells were stained for a panel of cell markers by incubation in PBS, 0.1% NaN2, 2% FBS for 20 min on ice by titrated concentrations of reagents. Cell-associated fluorescence was analyzed by an FACSCantoII flow cytometer and the DIVA V6 software (Becton Dickinson). Flow cytometry figures were buy GSK3235025 prepared using the FlowJo

Software (Tree Star, Ashland, OR, USA). Differences in lymphocyte populations were analyzed statistically with unpaired Student’s t-test using the Sigmaplot 9 statistical software. Immunoblotting assays were performed as previously described 28. Nuclear extracts were prepared Liothyronine Sodium by thymocytes and EMSA was performed as previously described 26. The sequences of the oligonucleotides used to detect Oct-1 DNA-binding activity were the following: Oct-1 F: 5′-TGT CGA ATG CAA ATC ACT AG-3 Oct-1 R: 5′-TTC TAG TGA TTT GCA TTC G-3′. The sequences of the oligonucleotides with two tandemly repeated NF-κB-binding sites (underlined) that were used to detect NF-κB DNA-binding activity were the following: NF-κBf: 5′-ATC AGG GAC TTT CCG CTG GGG ACT TT-3 NF-κBr: 5′-CGG AAA GTC CCC AGC GGA AAG TCC CT-3′. Total RNA was isolated from total thymocytes or DP cells with Trizol (Invitrogen, Carlsbad, CA, USA), and oligo-dT-primed cDNA was prepared using Improm Reverse Transcriptase (Promega, Madison, WI, USA) according to the manufacturer’s instructions. A. T. performed the experiments and analyzed the results. S. G. performed the FACS sorting and prepared the extracts that were used in the experiments presented in Supporting Information Fig. 3. A. T. and G. M. designed the experiments and wrote the manuscript. G. M. coordinated the research.

[70, 71] Nevertheless a definitive comparison between the TLO-inducing capacities of ILCs versus T and/or B cells in vivo has not yet been attempted. The precise mechanisms leading to stromal activation and TLO generation in multiple tissue sites are not yet fully defined. This includes doubt as to whether tissue stromal cells simply convert to a ‘lymphoid-like’ phenotype during inflammation,[72] AZD2014 or whether LTos in TLOs arise from distinct progenitors. The tools to begin assessing this second hypothesis have only recently been developed, with sophisticated genetic lineage tracing

and ablation systems leading to the identification of a pro-fibrotic stromal cell population in murine skin that arises during inflammation from a fetal progenitor developmentally distinct from muscle and skin tissue cells.[73] In addition, recent work has revealed that FDCs arise from perivascular platelet-derived growth factor receptor β+ stromal progenitors in lymphoid and non-lymphoid tissues, with this process occurring during chronic inflammation.[74] Interestingly, the development of LN stromal cell subsets from adipocyte precursors has been recently reported.[75] As chronic inflammation of the intestine is associated both with TLOs[76]

and substantial mesenteric fat deposits around the inflamed organ[77] it is possible that inflamed adipose tissue may provide precursors HSP assay that subsequently develop into TLO-associated stromal networks in the gut. The specific precursor(s) responsible for differentiating Beta adrenergic receptor kinase into the various stromal subsets remain elusive, but may well be tissue-specific and disease-specific. Fibroblast-like cells are a potential candidate; fibrocytes are capable of differentiating into FDCs and have been implicated in human inflammatory disease;[78-81] fibroblasts themselves are capable of expressing adhesion molecules and

producing homeostatic chemokines (so mimicking SLO stroma);[82] and large numbers of intestinal fibroblast-like cells up-regulate Podoplanin expression during intestinal inflammation.[72] Nevertheless, there is still much to be revealed about the specific stromal subsets and/or stromal alterations that underlie TLO generation during inflammation, including in the gut.[83] As Table 3 shows, the structural make up of TLOs varies. Most TLOs will develop supportive and effective B-cell zones, sometimes capable of antigen-driven B-cell maturation, somatic hypermutation and class-switching.[84] This can occur via FDC expression of activation-induced cytidine deaminase,[85] with these processes accompanied by significant lymphangiogenesis[86-88] and vascular remodelling.[56] The level of T-cell zone development varies greatly; although the CCL21 expression often observed in TLOs would suggest that T-cell-zone-associated LTos may be present.

6D and E). This finding shows that MPECs formed in the absence of type-I IFN signaling differentiated into functional memory CD8+ T cells. Thus, type-I IFN signaling influences the overall frequency but not the functionality of memory CD8+ T cells. In this study, we have elucidated the role of type-I IFN signaling on CD8+ T cells and its ability to act as a fate-determining differentiation factor in vivo. We found that CD8+ T cells lacking the ability to sense type-I IFN failed to form terminally differentiated SLECs following

an acute viral infection associated with abundant type-I IFN. IFNAR−/− P14 cells, despite demonstrating a reduced expansion potential, could form qualitatively equivalent memory cells compared with WT P14 cells, albeit at a much lower frequency

than their WT counterparts. Moreover, we showed in vivo and confirmed in vitro that type-I IFN signaling on CD8+ T cells leads to upregulation of T-bet which can drive the differentiation selleck of SLECs (Fig. 7). In summary, this study identifies type-I IFN as an important factor instructing the lineage choice toward the differentiation of SLECs in the context of an infection inducing a type-I IFN-dominated inflammatory cytokine milieu. The data presented here expand and complement our current knowledge about the factors involved in the differentiation of CD8+ T cells 25, 26, including both cell intrinsic factors 27, 28 such as T-bet 4, 24, 28–31 and eomesodermin 24, 31–33 as well as cell extrinsic differentiation factors, such as IL-2 15, 34, 35 and IL-12 4, 5, 28, 30. Much like this website IL-12, type-I IFN acts as a signal 3 cytokine promoting expansion, effector cell differentiation and survival of activated CD8+ T cells 36. As both of these cytokines can serve as differentiation factors for CD8+ T cells, the nature of the invading pathogen with respect to predominantly inducing one of those at the expense of the other 37, 38 determines which of these two cytokines will play a more important role in vivo. Of note, less redundancy between IL-12 and type-I IFN

has been found in humans and IL-12 seems to be the main signal driving CD8+ T-cell Leukotriene-A4 hydrolase effector differentiation, whereas type-I IFN enhances the development of memory CD8+ T cells 39. There is ample evidence in the literature that direct IL-12 signaling on activated CD8+ T cells enhances expansion and promotes transition toward an SLEC phenotype 3, 4, 13, 40, 41. An elegant study by Kaech and colleagues 4 further clarified these findings, identifying IL-12 as an important factor regulating memory CD8+ T-cell formation by establishing a gradient of T-bet expression. In particular, this report clearly showed that T-bet is necessary and sufficient to drive the formation of SLECs, with high T-bet expression leading to the differentiation into SLECs, and lower amounts of T-bet facilitating the formation of MPECs 4. This finding supports our in vivo results showing that following an acute LCMV8.