The initial response of CD4+ IL-4-producing cells

Naive CD4(+) T cells were reported to produce small amounts of IL-4 in vitro, which are implicated to be sufficient to initiate T(h)2 response in vivo. However, IL-4-producing naive CD4(+) T cells are difficult to study in vivo because they are present in low numbers shortly after the first antigen exposure. Here, we used IL-4/green fluorescence protein (GFP) reporter mice (G4 mice) to track the initial response of CD4(+) IL-4-producing cells. We first established a flow cytometry method to estimate the number of GFP(+) cells. We demonstrated the effectiveness of this method by showing that the responding CD4(+)GFP(+) cells exhibited an activated phenotype, possessed the capacity to express IL-5 and IL-13, but not IFN-gamma mRNA, and showed enhanced levels of GATA3 and c-maf mRNA expression. More importantly, we showed that the cell lines derived from FACS-sorted CD4(+)GFP(+) cells were antigen specific. By using this newly established method, we showed that the majority of responding GFP(+) cells were CD4(+) T cells. Our study provides direct ex vivo evidence to show that a small percent of CD4(+) T cells that have no previous experience of antigenic stimulation might produce IL-4 to initiate T(h)2 response.     

Dendritic cells partially abrogate the regulatory activity of CD4+CD25+ T cells present in the human peripheral blood

The factors that influence the functionality of human CD4(+)CD25(+) regulatory T cells are not well understood. We sought to characterize the effects of dendritic cells (DCs) on the in vitro regulatory activity of CD4(+)CD25(+) T cells obtained from peripheral blood of healthy human donors. Flow cytometry showed that a higher proportion of CD4(+)CD25(+(High)) T cells expressed surface glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) and CTL-associated antigen 4 than CD4(+)CD25(-) or CD4(+)CD25(+(Med-low)) T cells. Intracellular Foxp3 was equivalently expressed on CD4(+)CD25(+(All)), CD4(+)CD25(+(High)), CD4(+)CD25(+(Med-low)) and CD4(+)CD25(-) T cell populations, irrespective of GITR and CTL-associated antigen 4 expression. CD4(+)CD25(+) T cells were isolated and then cultured in vitro with CD4(+)CD25(-) responder T cells and stimulated with anti-CD3 antibodies, and immature dendritic cells (iDCs), mature dendritic cells (mDCs), PBMCs or PBMCs plus anti-CD28 antibodies to provide co-stimulation. In addition, secretion of the T(h)1 cytokine IFN-gamma, IL-2 and the immunoregulatory cytokines, IL-10 and transforming growth factor (TGF)-beta, were also assessed in these cultures. We found that iDCs and mDCs were capable of reversing the suppression of proliferation mediated by CD4(+)CD25(+) regulatory T cells. However, the reversal of suppression by DCs was not dependent upon the increase of IFN-gamma and IL-2 production or inhibition of IL-10 and/or TGF-beta production. Therefore, DCs are able to reverse the suppressive effect of regulatory T cells independent of cytokine production. These results suggest for the first time that human DCs possess unique abilities which allow them to influence the functions of regulatory T cells in order to provide fine-tuning in the regulation of T cell responses.     

IL-10 is involved in the suppression of experimental autoimmune encephalomyelitis by CD25+CD4+ regulatory T cells

CD25(+)CD4(+) regulatory T cells inhibit the activation of autoreactive T cells in vitro and in vivo, and suppress organ-specific autoimmune diseases. The mechanism of CD25(+)CD4(+) T cells in the regulation of experimental autoimmune encephalomyelitis (EAE) is poorly understood. To assess the role of CD25(+)CD4(+) T cells in EAE, SJL mice were immunized with myelin proteolipid protein (PLP)(139-151) to develop EAE and were treated with anti-CD25 mAb. Treatment with anti-CD25 antibody following immunization resulted in a significant enhancement of EAE disease severity and mortality. There was increased inflammation in the central nervous system (CNS) of anti-CD25 mAb-treated mice. Anti-CD25 antibody treatment caused a decrease in the percentage of CD25(+)CD4(+) T cells in blood, peripheral lymph node (LN) and spleen associated with increased production of IFN-gamma and a decrease in IL-10 production by LN cells stimulated with PLP(130-151) in vitro. In addition, transfer of CD25(+)CD4(+) regulatory T cells from naive SJL mice decreased the severity of active EAE. In vitro, anti-CD3-stimulated CD25(+)CD4(+) T cells from naive SJL mice secreted IL-10 and IL-10 soluble receptor (sR) partially reversed the in vitro suppressive activity of CD25(+)CD4(+) T cells. CD25(+)CD4(+) T cells from IL-10-deficient mice were unable to suppress active EAE. These findings demonstrate that CD25(+)CD4(+) T cells suppress pathogenic autoreactive T cells in actively induced EAE and suggest they may play an important natural regulatory function in controlling CNS autoimmune disease through a mechanism that involves IL-10.     

4-1BB co-stimulation enhances human CD8(+) T cell priming by augmenting the proliferation and survival of effector CD8(+) T cells

Interactions between 4-1BB and its ligand, 4-1BBL, enhance CD8(+) T cell-mediated antiviral and antitumor immunity in vivo. However, mechanisms regulating the priming of CD8(+) T cell responses by 4-1BB remain unclear, particularly in humans. The 4-1BB receptor was undetectable on naive or resting human CD8(+) T cells and induced in vitro by TCR triggering. Naive cord blood cells were therefore primed in vitro against peptides or cellular antigens and then co-stimulated with 4-1BBL or agonistic antibodies. Co-stimulation enhanced effector function such as IFN-gamma production and cytotoxicity by augmenting numbers of antigen-specific and effector CD8(+) T cells. OKT3 responses also showed reduced cell death and revealed that the proliferation of CD8(+) T cells required two independently regulated events. One, the induction of IL-2 production, could be directly triggered by 4-1BB engagement on CD8(+) T cells in the absence of accessory cells. The other, expression of CD25, was induced with variable efficacy by accessory cells. Thus, suboptimal accessory cells and 4-1BB co-stimulation combined their effects to enhance IL-2 production and proliferation. Reduced apoptosis observed after co-stimulation in the presence of accessory cells correlated with increased levels of Bcl-X(L) in CD8(+) T cells, while Bcl-2 expression remained unchanged. Altogether, 4-1BB enhanced expansion, survival and effector functions of newly primed CD8(+) T cells, acting in part directly on these cells. As 4-1BB triggering could be protracted from the TCR signal, 4-1BB agonists may function through these mechanisms to enhance or rescue suboptimal immune responses.     

Naive human T cells can be a source of IL-4 during primary immune responses

IL-4 plays a key role in driving the differentiation of CD4+ Th precursors into Th2 cells, both in mice and in humans. The source of IL-4 during primary immune responses is, however, still debated. When IL-4 consumption in in vitro T cell cultures was blocked with a MoAb to the IL-4 receptor alpha-chain (IL-4Ralpha), it became evident that freshly isolated naive (CD45RO-) CD4+ T cells from adults or cord blood produce IL-4 upon activation with anti-CD3 and CD80. IL-4 production by naive T cells is strictly IL-2-dependent. Endogenous IL-4 activity in naive CD4+ T cell cultures modulates the production of interferon-gamma (IFN-gamma) on the one hand and IL-5 and IL-13 on the other hand in opposite directions, and it is partly responsible for the low IFN-gamma production by cord blood T cells. Comparison of the ratio of IL-4/IFN-gamma in supernatants of T cell cultures reveals a skewing towards IL-4 production by cord blood T cells, while naive T cells from (non-atopic) adults predominantly produce IFN-gamma. We conclude that CD4+ naive T cells can produce IL-4 without the need for Th2 differentiation, and therefore that they can be the initial source of IL-4 required at the time of priming for T cell differentiation into Th2 cells.     

A role for dendritic cells in the priming of antigen-specific CD4+ and CD8+ T lymphocytes by immune-stimulating complexes in vivo

Immune-stimulating complexes (ISCOMS) are adjuvant vectors which are unusual in being able to prime both CD4(+) and CD8(+) T cells by parenteral and mucosal routes. However, their mode of action is unclear and to define better the cellular interactions involved we have studied the ability of ISCOMS containing ovalbumin (OVA) to prime TCR transgenic CD4(+) or CD8(+) T cells in vivo. Immunization with OVA ISCOMS caused activation and clonal expansion of CD4(+) and CD8(+) T cells in the T cell areas of the draining lymph nodes, followed by the migration of both CD4(+) and CD8(+) T cells into the B cell follicle. The T cells were primed to proliferate and secrete IFN-gamma after re-stimulation in vitro with the appropriate OVA peptide and CD8(+) T cell priming occurred in the absence of CD4(+) T cells. Increasing the number of dendritic cells (DC) in vivo with flt3 ligand augmented the expansion and activation of the OVA-specific T cells, particularly CD8(+) T cells. These studies indicate DC play a central role in the priming of both CD4(+) and CD8(+) T cells in vivo, and suggest that an ability to target DC may allow ISCOMS to be powerful vaccine vectors for stimulating protective immunity.     

Concomitant increase of IL-10 and pro-inflammatory cytokines in intraepithelial lymphocyte subsets in celiac disease

Celiac disease (CD) is a small intestinal enteropathy caused by permanent intolerance to wheat gluten. Active disease is characterized by a prominent cytokine response of intraepithelial lymphocytes (IELs) to gluten-containing diet with concomitant increase in expression of pro-inflammatory IFN-gamma and down-regulatory IL-10 without increase in tumor necrosis factor-alpha (TNF-alpha) or transforming growth factor-beta1 (TGF-beta1). The aim was to understand the local immune reaction by determining which intraepithelial T cell subsets produce the different cytokines. The three major IEL-subsets gammadeltaIELs, CD4(+)alphabetaIELs and CD8(+)alphabetaIELs, as well as CD94(+)CD8(+)alphabetaIELs, selectively expanded in active CD, were retrieved from small intestinal biopsies of children with active CD and controls and analyzed quantitatively for cytokine mRNA expression. In active CD, CD8(+)alphabetaIELs showed a significant increase in expression levels of both IFN-gamma and IL-10. CD8(+)alphabetaIELs were also the IEL subset with highest expression level per cell of both cytokines and constituted the cellular source for almost all IFN-gamma and most IL-10. Expression levels of both cytokines were higher in CD94(-)CD8(+)alphabetaIELs than CD94(+)CD8(+)alphabetaIELs. TNF-alpha levels were only increased in CD4(+)alphabetaIELs, which also showed the highest expression level per cell and constituted the major source of this cytokine. Interestingly, IL-10 was increased also in CD4(+)alphabetaIELs. Cytokine levels were low in gammadeltaIELs. 'Classical' CD94(-)CD8(+)alphabeta T cells within the epithelium are responsible for the excessive production of IFN-gamma, believed to drive the formation of intestinal lesions in active CD. Production of IL-10 may be a common feature of IELs producing pro-inflammatory cytokines, thereby attempting to limit inflammation in an autocrine fashion.     

Comparison of allergen-stimulated dendritic cells from atopic and nonatopic donors dissecting their effect on autologous naive and memory T helper cells of such donors

BACKGROUND: Because of their production of IL-12, mature dendritic cells (DC) are potent inducers of T(H)1 responses. However, recent reports have demonstrated that DCs can also induce T(H)2 differentiation. OBJECTIVE: In the current study we investigated which immune response is induced by DCs in naive CD45RA(+) or memory CD45R0(+) CD4(+) T cells from atopic individuals (patients with grass pollen, birch pollen, or house dust mite allergy) compared with nonatopic control subjects. METHODS: Immature DCs, generated from peripheral blood monocytes from atopic and nonatopic donors, were pulsed with the respective allergen and fully matured. Then the mature DCs were cocultured in vitro with autologous naive (CD45RA(+)) and memory (CD45R0(+)) CD4(+) T cells and cytokine and IgE production were measured by ELISA. RESULTS: After the second restimulation with allergen-pulsed DCs, naive as well as memory autologous CD4(+) T cells from atopic but not from nonatopic donors showed an enhanced production of the T(H)2-type cytokines IL-4, IL-5, and IL-10, resulting in an increased IgE production, whereas IFN-gamma production and proliferation were not different. IL-12 production and surface marker expression of DCs derived from atopic and nonatopic donors did not differ and addition of neutralizing anti-IL-12 mAbs did not increase IL-4 but diminished IFN-gamma production. CONCLUSION: These data indicate that mature DCs are able to induce naive and activate allergen-specific T helper cells to produce T(H)2 cytokines if the T cells are derived from atopic donors. This phenomenon is not due to diminished IL-12 production by DCs of atopic donors.     

A central role for IL-2 in fate determination of mature T cells--I: role in determining the Th1/Th2 profile in primary T cell cultures.

IL-2 signaling appears to play a significant role in enabling the synthesis of T(h)2 cytokines in an in vitro system for studying primary T cell responses. When T cells from C57BL/6J or BALB/c strains of mice were activated in vitro and re-stimulated through their TCR complex 48 h later, CD4(+) T cells producing the T(h)2 cytokines IL-4 and IL-10 were found only when IL-2 was present. IL-2 also enhanced IFN-gamma synthesis in C57BL/6J cells but not in BALB/c cells. By up-regulating production of anti-inflammatory T(h)2 cytokines during a primary response, IL-2 may play a critical role in limiting T(h)1-mediated responses.     

Mature dendritic cells differentiated in the presence of interferon-beta and interleukin-3 prime functional antigen-specific CD8 T cells

Dendritic cell (DC)-based immunization represents a promising approach for the immunotherapy of cancer. The optimal conditions required to prepare DCs remain to be defined. Monocytes incubated in the presence of interferon (IFN)-beta and interleukin (IL)-3 give rise to a distinct type of DCs (IFN-beta/IL-3 DCs) that are particularly efficient at eliciting IFN-gamma and IL-5 production by allogeneic helper T cells. We assessed the capacity of this new type of DCs to prime antigen-specific naive CD8(+) T cells and compared them to the conventional DCs differentiated in the presence of granulocyte-macrophage colony stimulating factor (GM-CSF) and IL-4 (GM-CSF/IL-4 DCs). We demonstrate that IFN-beta/IL-3 DCs matured by TLR3 or CD40 ligation efficiently prime Melan-A(26-35)-specific CD8(+) T cells in vitro, at a similar level as GM-CSF/IL-4 DCs. Activated antigen-specific CD8(+) T cells produced IFN-gamma and displayed potent cytotoxic activity against peptide-pulsed target cells. Expansion of CD8(+) T cell numbers was generally higher following priming with CD40-L than with polyinosinic-polycytidylic acid (poly I:C) matured DCs. Cytolytic activity was induced by both maturing agents. These data indicate that IFN-beta/IL-3 DCs represent a promising cell population for the immunotherapy of cancer.     

Requirement for IFN-gamma in IL-12 production induced by collaboration between v(alpha)14(+) NKT cells and antigen-presenting cells

Two cytokines IL-4 and IL-12 are known to determine the balance between T(h)1 and T(h)2 development. In addition to IL-4 production of V(alpha)14(+) NKT cells, they have recently been demonstrated to have the capacity to stimulate IL-12 production by antigen-presenting cells (APC). This study demonstrates that IFN-gamma is absolutely required for the NKT cell-stimulated IL-12 production. Culture of B cell-depleted spleen cells from C57BL/6 mice with alpha-galactosylceramide (alpha-GalCer) capable of selectively stimulating V(alpha)14/J(alpha)281(+) NKT cells resulted in the production of IL-12 together with IL-4. Whereas IL-4 production occurred in culture of IFN-gamma(-/-) C57BL/6 splenocytes, the same culture failed to generate IL-12 production. While IL-12 production induced during culture of V(alpha)14(+) NKT cells and APC depended on the interaction between CD40 ligand on NKT cells and CD40 on APC, the expression levels of these key molecules were comparable in cells from wild-type and IFN-gamma(-/-) mice. Addition of rIFN-gamma to alpha-GalCer stimulated IFN-gamma(-/-) splenocyte culture, and administration of rIFN-gamma to alpha-GalCer-injected IFN-gamma(-/-) mice resulted in the restoration of IL-12 production in vitro and in vivo. These results illustrate a mandatory role for IFN-gamma in V(alpha)14(+) NKT cell-stimulated IL-12 production by APC.     

Enhanced IL-10 production by CD4+ T cells primed in IL-15Rα-deficient mice

In this study, we investigated the functional outcomes of CD4(+) T cells primed in the absence of IL-15 transpresentation. Compared with their WT counterparts primed in WT mice, IL-15Rα KO CD4(+) T cells primed in KO mice were found to exclusively overproduce IL-10 upon in vitro restimulation(.) The comparable expression of IL-4 and Foxp3 in CD4(+) T cells primed in the WT and IL-15Rα KO mice indicated that this was neither due to T(H) 2- nor Treg cell-differentiation. IL-10 overproduction was also observed when OVA-specific TCR transgenic CD4(+) T (OT-II) cells were primed in KO mice, excluding an intrinsic deficiency of KO CD4(+) T cells. To investigate the WT and KO microenvironment, DCs from both WT and IL-15Rα KO mice were compared. DCs from both backgrounds were indistinguishable in their steady-state survival and in their expression of MHC class II and costimulatory molecules CD80, CD86, and CD40. However, IL-15Rα KO DCs primed OT-II cells in vitro to produce higher levels of IL-10 upon their restimulation. Additionally, IL-15Rα KO DCs produced significantly more IL-10 upon activation, and IL-10 neutralization during DC-mediated in vitro priming abolished IL-10 overproduction by CD4(+) T cells. Thus, IL-15Rα KO DCs provide an IL-10-enriched environment that preferentially primes CD4(+) T cells for more IL-10 production, highlighting a regulatory role for IL-15 transpresentation in CD4(+) T-cell priming.     

Th2 bias of CD4+ NKT cells derived from multiple sclerosis in remission

Although CD1d-restricted NKT cells have been implicated as a participant in the regulatory mechanism of autoimmune diseases, it remains unclear how they would regulate human autoimmune diseases such as multiple sclerosis (MS). Furthermore, although the NKT cells comprise CD4(+) and CD4(-) populations, prior studies have often represented them as simply a CD4(-) population. Given that CD4(+) and CD4(-) NKT cells may represent functionally distinct populations, it appears crucial to examine the individual NKT subset in autoimmune diseases. Here we studied the frequency and cytokine phenotypes of the CD4(+) and CD4(-) NKT cells in fresh peripheral blood mononuclear cells, and of alpha-galactosylceramide-stimulated short-term cell lines obtained during the remission or relapse phase of MS as compared with from healthy subjects (HS). Here we report that CD4(+) NKT line cells expanded from MS in remission (MS-rem) would produce a larger amount of IL-4 than those from HS or from MS in relapse (MS-rel). They were significantly biased for T(h)2 as judged by the IL-4/IFN-gamma balance. However, there was no functional bias toward T(h)1 or T(h)2 in CD4(-) NKT line cells from MS-rem due to the defects in both IFN-gamma and IL-4 production, compared with HS. Of note, although double-negative NKT cells in the periphery were greatly reduced, the reduction of CD4(+) NKT cells was only marginal, if any, in MS-rem compared with HS. The T(h)2 bias of CD4(+) NKT line cells from MS-rem may support an immunoregulatory role for the CD4(+) NKT cells in vivo.     

Early in vitro priming of distinct T(h) cell subsets determines polarized growth of visceralizing Leishmania in macrophages

An in vitro priming system of murine naive splenocytes was established to investigate early immune responses to LEISHMANIA: chagasi, the agent of visceral leishmaniasis in the New World. Priming of splenocytes from resistant C3H and CBA or susceptible BALB and B10 mice with L. chagasi resulted in blast transformation and in proliferating parasite-specific CD4(+) T cells secreting a differential complement of cytokines (IFN-gamma and low IL-10 levels for resistant T cells; IFN-gamma, IL-4 and high IL-10 levels for susceptible T cells). After priming, intracellular parasite load was much higher in susceptible than in resistant-type splenocyte cultures. On the other hand, infection of purified splenic macrophages from either resistant or susceptible mice with live L. chagasi promastigotes, resulted in comparable parasite loads. Moreover, when early CD4(+) T cell priming in splenocyte cultures was disrupted with anti-CD4 mAb, polarized parasite growth was abolished, becoming comparable in resistant and susceptible cultures. Neutralizing IL-4 activity during splenocyte priming did not affect the final parasite load in susceptible cultures. However, neutralizing IL-10 activity markedly decreased parasite load in susceptible, but not in resistant splenic macrophages. These results suggest that IL-10 plays an important role in L. chagasi infection in susceptible hosts. The results also indicate that innate control of growth of a visceralizing LEISHMANIA: in splenic macrophages results from the ability to activate different CD4(+) T cell subsets.     

Type 1 cytokine/chemokine production by mouse NK cells following activation of their TLR/MyD88-mediated pathways

It is well established that IL-18R- and toll-like receptor (TLR)-mediated signalings share a common signal pathway mediated by signal adaptor, MyD88, and that IL-18 synergizes with IL-12 for IFN-gamma production by NK cells. Here, we investigated whether TLR agonists can replace IL-18 for production of IFN-gamma by NK cells. Freshly isolated NK cells possessed functional LPS receptor composed of TLR4/MD2 complex and of CD14, and also expressed other various tlrs. Hepatic CD3(-)DX5(+) NK cells produced IFN-gamma in response to TLR2 or TLR7 agonists only when co-stimulated with IL-12, indicating that TLR agonists synergize with IL-12 for IFN-gamma. The tlr2(-/-) or tlr7(-/-) NK cells could not produce IFN-gamma in response to IL-12 plus TLR2 or TLR7 ligands, respectively, indicating requirement of the corresponding TLRs. Furthermore, upon stimulation with these combinations, wild-type NK cells produced type 1 chemokines, such as CCL3, CCL4 and CCL5 as well. NK cells from bacterium (e.g. Propionibacterium acnes)-inoculated rag2(-/-) mice, when compared with those from naive mice, exhibited significantly enhanced capacity to produce these CC chemokines and IFN-gamma, suggesting that microbial infection enhances responsiveness of NK cells to TLR agonists. These results indicate that upon microbial infection, macrophages produce IL-12 that renders NK cells highly responsive to TLR agonists to produce IFN-gamma and chemokines, which might in turn recruit and fully activate macrophages, leading to the development of inflammatory foci presumably necessary for efficient microbial eradication. Thus, NK cells, like T cells, induce orchestrated immune responses in collaboration with macrophages to show potent host defense effects during early infectious phase.     

Neonatal dendritic cells are intrinsically biased against Th-1 immune responses

Dendritic cells (DCs) were derived from human peripheral blood monocytes or cord blood monocytes cultured in the presence of IL-4 and GM-CSF. Adult and cord DCs were observed to have comparable immature phenotypes. However, the increase in surface expression of HLA-DR and CD86 after addition of LPS was significantly attenuated in cord DCs, with CD25 and CD83 expression also markedly reduced. Cord DCs were also unable to produce IL-12p70, failed to down-regulate expression of the chemokine receptor CCR5 and induced lower levels of IFN-gamma production from allogeneic naive CD4+ T cells than their adult counterparts. In contrast, the kinetics of the production of TNF-alpha and IL-10 in response to LPS stimulation was comparable to adult DCs. The reduced ability of cord DCs to attain a fully mature adult phenotype, and to activate naive CD4+ T cells to produce IFN-gamma, suggests that they are intrinsically preprogrammed against the generation of Th-1 immune responses.     

IL-12 synergizes with IL-18 or IL-1beta for IFN-gamma production from human T cells

IL-18 is a proinflammatory cytokine that plays an important role in NK cell activation and T(h)1 response. IL-18 has a structural homology to IL-1, particularly IL-1beta. IL-18R, composed of IL-1R-related protein (IL-18Ralpha) and IL-1R accessory protein-like (IL-18Rbeta), belongs to the IL-1R family. Furthermore, IL-18R at least partly shares the signal transducing system with IL-1R. Thus, the IL-18-IL-18R system has a striking similarity to the IL-1-IL-1R system. For this reason, we regarded it important to investigate whether, like IL-18, IL-1beta synergizes with IL-12 in inducing IFN-gamma production from human T cells and plays an important role in the T(h)1 response. Here we show that IL-12 and IL-1beta synergistically induce T cells to proliferate and produce IFN-gamma without their TCR engagement. IL-12 stimulation induced an increase in the proportion of T cells positive for IL-18R. Then, IL-12-stimulated T cells responded to IL-18 or IL-1beta by their proliferation and IFN-gamma production, although levels of IL-1beta-induced responses were lower. CD4(+)CD45RA(+) T cells, although they constitutively expressed IL-18Rbeta mRNA, did not express IL-18Ralpha mRNA. Phytohemagglutinin (PHA) stimulation alone induced IL-18Ralpha mRNA without affecting the expression of IL-18Rbeta mRNA. T(h)1-inducing conditions (PHA, IL-12 and anti-IL-4) further increased this expression. We also show that T(h)1 cells but not T(h)2 cells have increased expression of IL-18R and IL-1R, and produce IFN-gamma in response to IL-18 and/or IL-1beta.     

Instruction of naive CD4+ T-cell fate to T-bet expression and T helper 1 development: roles of T-cell receptor-mediated signals

Using T-cell receptor (TCR) transgenic mice, we demonstrate that TCR stimulation of naive CD4(+) T cells induces transient T-bet expression, interleukin (IL)-12 receptor beta2 up-regulation, and GATA-3 down-regulation, which leads to T helper (Th)1 differentiation even when the cells are stimulated with peptide-loaded I-A(b)-transfected Chinese hamster ovary cells in the absence of interferon-gamma (IFN-gamma) and IL-12. Sustained IFN-gamma and IL-12 stimulation augments naive T-cell differentiation into Th1 cells. Intriguingly, a significant Th1 response is observed even when T-bet(-/-) naive CD4(+) T cells are stimulated through TCR in the absence of IFN-gamma or IL-12. Stimulation of naive CD4(+) T cells in the absence of IFN-gamma or IL-12 with altered peptide ligand, whose avidity to the TCR is lower than that of original peptide, fails to up-regulate transient T-bet expression, sustains GATA-3 expression, and induces differentiation into Th2 cells. These results support the notion that direct interaction between TCR and peptide-loaded antigen-presenting cells, even in the absence of T-bet expression and costimulatory signals, primarily determine the fate of naive CD4(+) T cells to Th1 cells.