Interleukin-12 but not interferon-γ production correlates with induction of T helper type-1 phenotype in murine candidiasis

By means of polymerase chain reaction-assisted mRNA amplification, we have monitored message levels of interleukin (IL)-12 in splenic macrophages and of interferon-γ (IFN-γ), IL-4, and IL-10 in CD4⁺ and CD8⁺ T cells using Candida albicans/host combinations that result either in a T helper type-1 (Th1)-associated self-limiting infection (“healer mice”) or in a Th2-associated progressive disease (“nonhealer mice”). The timing and pattern of message detection did not differ qualitatively by the expression of IFN-γ or IL-10 mRNA in CD4⁺ and CD8⁺ cells from healer (i.e. PCA-2 into CD2F1) vs. nonhealer (i.e. CA-6 into CD2F1 or PCA-2 into DBA/2) mice. In contrast, IL-4 mRNA was uniquely expressed by CD4⁺ cells from nonhealer animals. IL-12p40 was readily detected in macrophages from healer mice but was detected only early in infection in mice with progressive disease. Cytokine levels were measured in sera, and antigen-driven cytokine production by CD4⁺ and CD8⁺ cells was assessed in vitro, while IFN-γ-producing cells were enumerated in CD4^? CD8^? cell fractions. Overall, our results showed that (i) antigen-specific secretion of IFN-γ protein in vitro by CD4⁺ cells occurred only in healing infection; (ii) IL-4- and IL-10-producing CD4⁺ cells would expand in nonhealer mice in the face of high levels of circulating IFN-γ, likely released by CD4^? CD8^? lymphocytes; (iii) a finely regulated IFN-γ production correlated in the healer mice with IL-12 mRNA detection, and IL-12 was required in vitro for yeast-induced development of IFN-γ-producing CD4⁺ cells. Although the mutually exclusive production of IL-4/IL-10 and IFN-γ by early CD4⁺ cells may be the major discriminative factor of cure and noncure responses in candidiasis, IL-12 rather than IFN-γ production may be an indicator of Th1 differentiation.     

Interferon-γ- and interleukin-4-producing T cells can be primed on dendritic cells in vivo and do not require the presence of B cells

The antigen-presenting cell (APC) requirements for the in vivo induction of Th1-and Th2-type responses were investigated using a severe combined immunodeficiency (SCID)mouse chimera model. SCID mice adoptively transferred with either T cells [SCID(T)] or T + B cells [SCID(T + B)] and immunized with antigen in adjuvant were able to generate antigen-specific T cells which could produce both interferon (IFN)-γ and interleukin (IL)-4 upon in vitro restimulation. This suggests that B cell APC are not necessary for the priming of either IFN-γ- or IL-4-producing T cells in vivo. The ability of different APC to activate Th2-dependent effector mechanisms was also investigated. SCID(T) and SCID(T + B) mice were infected with the nematode parasite Nippostrongylus brasiliensis and analyzed for the development of IL-5-dependent peripheral blood eosinophilia. Following infection both SCID(T) and SCID(T + B) mice generated similar numbers of peripheral blood eosilnophils, suggesting that similar amounts of IL-5 had been produced. Therefore, B cell APC are also not required for the in vivo activation of Th2 cells to lymphokine production. To establish more precisely which APC prime T cells to produce IFN-γ and IL-4, normal mice were immunized by injection of syngeneic splenic dendritic cells which had been pulsed with antigen in vitro. T cells from these immunized mice were able to produce good IFN-γ and IL-4 responses upon in vitro restimulation with specific antigen; therefore, dendritic cells appear to be sufficient APC for the in vivo priming of both IFN-γ- and IL-4-producing T cells.     

Anti-IL-12 antibody prevents the development and progression of collagen-induced arthritis in IFN-γ receptor-deficient mice

In several models of inflammation, including collagen-induced arthritis (CIA), the disease-promoting effect of IL-12 has been attributed to its well-known ability to produce IFN-γ. However, IFN-γ receptor knockout (IFN-γ R KO) mice of the DBA/1 strain have been reported to be more susceptible to CIA than corresponding wild-type mice, indicating the existence of an IFN-γ-mediated protective pathway in this model. In the present study the development of CIA was found to be completely prevented by pretreatment with a neutralizing anti-IL-12 antibody, not only in wild-type, but significantly also in IFN-γ R KO mice. In both strains of mice, the protective effect of anti-IL-12 was associated with lower production of anti-collagen type II antibodies. In vivo stimulation with anti-CD3 antibody in arthritic IFN-γ R KO mice resulted in production of higher levels of circulating IFN-γ, TNF and IL-2 than in corresponding control mice that had not received the arthritis-inducing immunization. This was not the case in arthritis-developing wild-type mice. Furthermore, the protective effect of anti-IL-12 antibody in mutant, but not in wild-type mice, was associated with lower circulating IFN-γ, TNF and IL-2 and higher IL-4 and IL-5 cytokine levels following an anti-CD3 challenge. The data indicate that IL-12 promotes the development of arthritis independently of its ability to induce or favor production of IFN-γ. In fact, any IFN-γ produced in the course of the disease process rather exerts a protective effect. Furthermore, our study suggests that, in the absence of a functional IFN-γ system, endogenous IL-12 exerts its disease-promoting effect by favoring production of other Th1-associated cytokines (IL-2 and TNF), by inhibiting development of IL-4- and IL-5-producing T cells and by stimulating production of anti-collagen autoantibodies.     

IL-4-producing NK T cells are biased towards IFN-γ production by IL-12. Influence of the microenvironment on the functional capacities of NK T cells

NK T cells are an unusual T lymphocyte subset capable of promptly producing several cytokines after stimulation, in particular IL-4, thus suggesting their influence in Th2 lineage commitment. In this study we demonstrate that, according to the cytokines present in the micro environment, NK T lymphocytes can preferentially produce either IL-4 or IFN-γ. In agreement with our previous reports showing that their IL-4-producing capacity is strikingly dependent on IL-7, CD4⁻ CD8⁻ TCRα β⁺ NK T lymphocytes, obtained after expansion with IL-1 plus granulocyte-macrophage colony-stimulating factor, produced almost undetectable amounts of IL-4 or IFN-γ in response to TCR/CD3 cross-linking. However, the capacity of these T cells to produce IFN-γ is strikingly enhanced when IL-12 is added either during their expansion or the anti-CD3 stimulation, while IL-4 secretion is always absent. A similar effect of IL-12 on IFN-γ production was observed when NK T lymphocytes were obtained after expansion with IL-7. It is noteworthy that whatever cytokines are used for their expansion, IL-12 stimulation, in the absence of TCR/CD3 cross-linking, promotes consistent IFN-γ secretion by NK T cells without detectable IL-4 production. Experiments in vivo demonstrated a significant up-regulation of the capacity of NK T cells to produce IFN-γ after anti-CD3 mAb injection when mice were previously treated with IL-12. In conclusion, we provide evidence that the functional capacities of NK T cells, which ultimately will determine their physiological roles, are strikingly dependent on the cytokines present in their microenvironment.     

Kinetics of IL-17- and interferon-γ-producing PLPp-specific CD4 T cells in EAE induced by coinjection of PLPp/IFA with pertussis toxin in SJL mice

Systemic administration of Pertussis toxin (PTX) abrogates T cell tolerance mediated by injection of neuroantigens in incomplete Freund's adjuvant (IFA) and causes experimental autoimmune encephalomyelitis (EAE). PTX concomitantly induces high frequencies of neuroantigen-specific IFN-γ- and IL-17-producing T cells. Both IL-17 and IFN-γ have been implicated as a key effector cytokines in the pathogenesis of EAE, possibly with different functions. We therefore investigated potential differences in the temporal and spatial kinetics of the PTX-induced neuroantigen-specific IFN-γ- and IL-17-producing T cell effector populations. IFN-γ- and IL-17-producing PLPp-specific T cells initially arose in comparable frequencies in the local draining lymph nodes (drLN) after immunization as measured by cytokine ELISPOT. High frequencies of both IFN-γ- and IL-17-producing T cells were present in the immune periphery before onset of EAE. The highest frequencies of PTX-induced IFN-γ- and IL-17-producing PLPp-specific cells coincided in the inflamed CNS during acute EAE. During recovery, both IFN-γ- and IL-17-producing PLPp-specific T cells simultaneously disappeared from the CNS, whereas high frequencies of these cells remained present in the immune periphery. The functional affinity of both IFN-γ- and IL-17-producing T cells did not change during EAE. Therefore, autoimmune pathology in this model did not correlate with specific PTX effects either on Th1 or Th17 cells regarding their kinetics and CNS migration.     

Increased Frequency of Cells Secreting Interleukin-6 and Interleukin-10 in Peripheral Blood of Patients with Primary Sjögren''s Syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease of exocrine glands. There is increasing evidence that interferon-γ (IFN-γ) plays a role in the pathogenesis of SS. It has also been suggested that other type 1 cytokines, as well as interleukin-6 (IL-6), IL-10 and transforming growth factor-β, are important in the induction and/or maintenance of SS. The aim of this study was to investigate the type 1/type 2 cytokine pattern in peripheral blood of primary SS patients. The enzyme-linked immunospot (ELISPOT) assay was performed to quantify the number of mononuclear cells (MNC) secreting IFN-γ, IL-6 and IL-10 in peripheral blood samples from 33 patients with primary SS and 12 healthy controls. The mean number of cells secreting IFN-γ was 9/10⁵ MNC in the SS patient group, and 4/10⁵ MNC in the control group (P = 0.73). Fifteen of the SS patients had anti-Ro 52 kDa antibodies in serum. In this patient group the mean number of cells secreting IFN-γ was 4/10⁵ MNC, while in the patient group without such antibodies the mean number of cells secreting IFN-γ was 14/10⁵ MNC (P = 0.04). The mean number of cells secreting IL-6 was 12 000/10⁵ MNC in the SS patient group, and 5000/10⁵ MNC in the control group (P = 0.01). The mean number of cells secreting IL-10 was 270/10⁵ MNC in the SS patient group, and 180/10⁵ MNC in the control group (P = 0.04). The SS patients had a significantly higher number of cells secreting IL-6 and IL-10 in peripheral blood than the healthy controls, which may facilitate B-cell activation and production of autoantibodies.     

Sequential production of IL-2, IFN-γ and IL-10 by individual staphylococcal enterotoxin B-activated T helper lymphocytes

Upon primary activation, T helper (Th) cell populations express different cytokines transiently and with different kinetics. Stimulation of naive murine splenic Th cells with the bacterial superantigen Staphylococcus aureus enterotoxin B (SEB) in vitro results in expression of IL-2, IFN-γ and IL-10 with fast, intermediate and slow kinetics, respectively. This first report of a functional analysis of cells separated alive according to cytokine expression shows that these cytokines are not produced by different Th cell subpopulations, but can be expressed sequentially by individual Th cells. Th cells, activated with SEB for 1 day and isolated according to expression of IL-2, using the cellular affinity matrix technology, upon continued stimulation with SEB later secrete most of the IFN-γ and IL-10. Likewise, after 2 days of SEB culture, cells expressing IFN-γ, separated according to specific surface-associated IFN-γ as detected by magnetofluorescent liposomes, 1 day later secrete IL-10. Thus, individual Th1 cells can contribute to the control of their own IFN-γ expression by sequential expression of first IL-2, supporting their proliferation, and later IL-10, down-regulating the production of IFN-γ-inducing monokines and limiting the pro-inflammatory effects of IFN-γ.     

Regulation of T helper cell differentiation in vivo by soluble and membrane proteins provided by antigen-presenting cells

The aim of this study was to test whether the nature of the antigen-presenting cell (APC) can influence the Th1 / Th2 balance in vivo. Our data show that dendritic cells (DC), pulsed extra corporeally with antigen, induced the development of cells secreting IL-2, IFN-γ and IL-4 upon antigen rechallenge in vitro. Priming with peritoneal macrophages sensitized cells that produced IL-4 but not IFN-γ. To identify the factors involved in T helper development, mice were primed with APC with or without treatment with neutralizing antibodies to co-stimulatory molecules or cytokines. Our results indicate that priming with DC or macrophages is strictly dependent on the CD28-CTLA4/ B7 interaction. Of note, CD86 provides the initial signal to induce naive T cells to become IL-4 producers, whereas CD80 is a more neutral differentiation signal. IL-12, released by the DC, appears as a potent and obligatory inducer of differentiation for IFN-γ-producing cells. IL-6, although produced by both APC populations, is necessary to direct activation of the Th2-type response by macrophages but not by DC.     

Flow cytometric determination of cytokines in activated murine T helper lymphocytes: Expression of interleukin-10 in interferon-γ and in interleukin-4-expressing cells

In an immune response, effector functions are controlled by T helper (Th) 1 cytokines [interferon-γ (IFN-γ), interleukin (IL)-2 and tumor necrosis factor-β] and Th 2 cytokines (IL-4, IL-5 and IL-10). Here we analyze by multiparameter immunofluorescence to what extent IL-2, IL-4, IL-5, IL-10 and IFN-γ are co-expressed in individual normal murine Th cells upon activation in vitro with the bacterial superantigen Staphylococcus aureus enterotoxin B, presented in the context of major histocompatibility complex class II. IL-2 and IFN-γ are co-expressed by some, but not by other Th cells. Expression of IL-4 and IFN-γ is exclusive. IL-10 is co-expressed in individual cells either with IL-4 or with IFN-γ. No IL-5-expressing cells are detected. While IL-10- and IL-4-co-expressing Th cells correspond to classical Th 2 cells, cells co-expressing IL-10 and IFN-γ could be involved in negative-feedback regulation of a Th 1 response. Apart from such functional implications, our results show that IL-2, IL-4, IL-5, IL-10 and IFN-γ are expressed independently of each other in individual murine Th cells.     

Association of T-cell reactivity with β-cell function in recent onset type 1 diabetes patients

ObjectiveThe aim of the current study was to investigate whether autoantigen directed T-cell reactivity relates to β-cell function during the first 78 weeks after diagnosis of type 1 diabetes.Research design and methods50 adults and 49 children (mean age 27.3 and 10.9 years respectively) with recent onset type 1 diabetes who participated in a placebo-controlled trial of immune intervention with DiaPep277 were analyzed. Secretion of interferon (IFN)-γ, interleukin (IL)-5, IL-13 and IL-10 by single peripheral mononuclear cells (PBMC) upon stimulation with islet antigens GAD65, heat shock protein 60 (Hsp60) protein-tyrosine-phosphatase-like-antigen (pIA2) or tetanus toxoid (TT) was determined applying ELISPOT; β-cell function was evaluated by glucagon stimulated C-peptide. Multivariate regression analysis was applied.ResultsIn general, number of islet antigen-reactive cells decreased over 78 weeks in both adults and children, whereas reactivity to TT was not reduced. In addition, there was an association between the quality of immune cell responses and β-cell function. Overall, increased responses by IFN-γ secreting cells were associated with lower β-cell function whereas IL-5, IL-13 and IL-10 cytokine responses were positively associated with β-cell function in adults and children. Essentially, the same results were obtained with three different models of regression analysis.ConclusionsThe number of detectable islet-reactive immune cells decreases within 1–2 years after diagnosis of type 1 diabetes. Cytokine production by antigen-specific PBMC reactivity is related to β-cell function as measured by stimulated C-peptide. Cellular immunity appears to regress soon after disease diagnosis and begin of insulin therapy.     

Cytokine synthesis analyzed at the single-cell level before and after revaccination with tetanus toxoid

Tetanus toxoid (TT) is a potent immunogen which evokes strong antibody responses after immunization. Here, TT was used as a model antigen to study the production of cytokines at the single-cell level during the in vitro immune response to a specific recall antigen. Peripheral blood mononuclear cells were obtained from healthy volunteers before and 9 weeks after TT vaccination and were cultured with antigen in vitro. The kinetics of cytokine synthesis as well as frequencies of cytokine-producing cells were determined at the single-cell level by immunofluorescent intracellular staining of the cytokine protein. The phenotype of the producer cells was revealed by concomitant staining of surface markers. Two patterns of cytokine synthesis were induced by TT: (i) T lymphocytes expressed a number of lymphokines (interleukin (IL)-2, IL-3, IL-4, IL-10, interferon (IFN)-γ and tumor necrosis factor (TNF)-β), each with distinct kinetics of synthesis. This cytokine expression was strictly dependent on the previous exposure of the donor to TT and positively correlated with the level of tetanus immunity, as judged by TT-specific Ab levels in plasma as well as lymphoproliferation. Cells producing IL-2, IFN-γ and particularly TNF-β dominated this in vitro response. After 96–120 h in culture, 1.0–1.3% of the cells produced TNF-β, i.e. frequencies at least tenfold higher than for any of the other lymphokines assayed. The addition of IL-2 to the cultures caused a fourfold increase and a kinetics shift in the production of TNF-β, which peaked already at 24 h. Exogenously added IL-2 also caused a five- to tenfold increase in the number of IL-2 and IFN-γ producers but no apparent change in the kinetics of intracellular lymphokine appearance. (ii) The cytokines IL-1α, IL-1β, IL-6 and TNF-α were produced by monocytes. This inflammatory monokine response was independent of the TT-specific immune status of the donors, characterized by a rapid onset and was transient.     

Interleukin-12 increases interleukin-4 production by established human ThO and Th2-like T cell clones

Interleukin (IL)-12 is a potent inducer of cell-mediated immunity: it favors the generation of interferon (IFN)-γ-producing T cells, increases IFN-γ production by T cells and natural killer cells and prevents the generation of a Th2 response in murine in vivo models. Nevertheless, the effects of IL-12 on an established Th2 response remain poorly documented. In the present paper, we analyzed the effect of IL-12 on the profile of lymphokines produced by established IL-4-producing Th0 and Th2-like human T cell clones (TCC) and by polyclonal T cells. We found that IL-12 (i) enhances, as previously reported, IFN-γ production by Th0 TCC and, to a smaller extent, by Th2-like TCC, (ii) increases the proliferation of Th0 and Th2-like TCC and (iii) unexpectedly, synergizes with T cell receptor-associated or nonspecific stimuli in increasing IL-4 production by these TCC. Thus, IL-12 potentiates the production of IFN-γ and also of IL-4 by established IL-4-producing TCC. Although IL-12 has been widely reported to induce a Th1 response and to prevent the development of a Th2 response in vivo, IL-12 may on the contrary potentiate an established Th2 response in humans.     

Specific expression of surface interferon-γ on interferon-γ producing T cells from mouse and man

Interferon (IFN)-γ is a potent immunoregulatory protein secreted by CD4⁺ and CD8⁺ T cells and by natural killer cells. Here, we show that IFN-γ is specifically displayed at a low concentration on the cell surface of those activated T cells from mouse and man which express IFN-γ. It is transiently expressed on the cell surface with kinetics similar to those of intracellular IFN-γ expression. Detectable surface IFN-γ is not expressed by activated T helper (Th) cells producing other cytokines but which do not express IFN-γ. Thus, surface IFN-γ is the first available marker for live T lymphocytes expressing IFN-γ, e.g. Th1 cells.     

IL-17/IFN-γ double producing CD8+ T (Tc17/IFN-γ) cells: a novel cytotoxic T-cell subset converted from Tc17 cells by IL-12

It has been reported that IFN-γ-producing CD8(+) T (Tc1) cells express cytotoxic molecules such as perforin and granzyme B to exhibit higher cytotoxicity against tumor cells compared with Tc2 cells. However, the critical role of IL-17-producing CD8(+) T (Tc17)-cell subsets in tumor immunity remains unclear. Tc17 cells differentiated from naive CD8(+) T cells did not possess cytotoxic molecules and exhibited no strong cytotoxicity. However, when Tc17 effector cells were further cultured with IL-12, they converted into IFN-γ-producing Tc17 cells, which mainly consisted of IL-17/IFN-γ double-producing cells (Tc17/IFN-γ). IL-12-converted Tc17 cells also acquired cytotoxic function in addition to IFN-γ producibility. Moreover, they showed strong anti-tumor activity both in vitro and in vivo as well as Tc1 cells. Among four distinct subsets in IL-12-converted Tc17 cell populations, the isolated Tc17/IFN-γ cells exhibited cytotoxicity as well as IFN-γ-producing Tc1-like cells. Thus, we first indicate direct evidence that Tc17/IFN-γ cells, which were plastically converted from non-cytotoxic Tc17 cells by IL-12, exhibited strong anti-tumor activity as well as Tc17 cell-derived Tc1-like cells.     

T cell response in murine Leishmanial mexicana amazonensis infection: production of interferon-γby CD8+ cells

The immune response to Leishmania major has been the subject of many investigations. However, Leishmania includes many species with different clinical manifestations. In this report, we studied the Tcell response to L. mexicana amazonensis, a New World species, in a murine model. We found that, similar to L. major, an Old World species, resistant C57BL/6 mice produced a high level of IFN-γ and a low level of IL-4. Conversely, susceptible BALB/c mice produced a much lower level of IFN-γ and higher level of IL-4. Although IFN-γ is one of the important lymphokines that mediate macrophage activation and thus the destruction of the intracellular parasites, which lymphocyte subsets are producing the IFN-γ is still a controversy. Much evidence including the isolation of protective, IFN-γ-producing, CD4⁺ cell lines have confirmed the participation of CD4⁺ Thl cells unequivocally. However, both CD4⁺ and CD8⁺ cells produced IFN-γ. Recently, an increasing body of evidence has appeared suggesting that CD8⁺ cells also play a role in the resolution of murine L. major infection. We found that in the L. m. amazonensis model, when CD8⁺ lymphocytes from resistant C57BL/6 mice were eliminated by anti-CD8 antibody and complement-mediated lysis, the IFN-γ production was reduced by 77%. This indicated that CD8⁺ cells produced a significant amount of the IFN-γ. However, our results also indicate that IFN-γ production by CD8⁺ cells was dependent on CD4⁺ cells.     

Normal B cells fail to secrete interleukin-12

Interleukin-12 is a key regulatory cytokine produced by antigen-presenting cells (APC) which drives the development of interferon-γ (IFN-γ)-producing cells and promotes cell-mediated immunity. Following subcutaneous immunization with protein antigen in adjuvant, dendritic cells (DC) but not small nor large B cells in immune lymph nodes express antigenic complexes and secrete substantial amounts of bioactive IL-12 p75 upon antigen-specific interaction with T cells. We have analyzed secretion of IL-12 p40 and p75 by cell populations enriched in DC, macrophages or B cells in response to nonspecific stimulation or to interaction with antigen-specific CD4⁺ cells. These APC populations do not produce IL-12 constitutively but, upon stimulation with heat-fixed Staphylococcus aureus and IFN-γ, IL-12 p40 and p75 are secreted by DC and macrophages, whereas B cells fail to produce IL-12. B cells also fail to secrete IL-12 in response to stimulation with LPS and IFN-γ. Co-culture with CD4⁺ T hybridoma cells and antigen induces IL-12 secretion by DC. Up-regulation of IL-12 secretion by interaction with antigen-specific CD4⁺ T cells is abrogated by anti-class II monoclonal antibodies (mAb), by soluble CD40 molecules and by anti-CD40 ligand mAb, demonstrating a positive feedback between T cells and DC mediated by TCR-peptide/class II and by CD40-CD40 ligand interactions. Expression of class II and CD40 molecules is comparable in B cells and DC, and both APC types activate CD4⁺ T cells. Yet, even upon interaction with antigen-specific T cells, B cells fail to secrete IL-12. The capacity of B cells to present antigen but not to secrete IL-12 may explain their propensity to selectively drive T helper type 2 cell development.