Differential effects of interleukin-12 on the development of naive mouse CD4+ T cells

Cytokine Kinetics during Progression of COVID-19 in Rwanda Patients: Could IL-9/IFNγ Ratio Predict Disease Severity?

For effective treatments and preventive measures against severe COVID-19, it is essential to determine early markers of disease severity in different populations. We analysed the cytokine kinetics of 129 COVID-19 patients with mild symptoms, 68 severe cases, and 20 healthy controls for the first time in Rwanda. Pro-inflammatory (IFNγ, IL-6, TNFα), Treg (IL-10, TGFβ1, TGFβ3), Th9 (IL-9), Th17 (IL-17), and Th2 (IL-4, IL-13) cytokines, total IgM and IgG, as well as gene expressions of FoxP3, STAT5+, IFNγ-R1, and ROR alpha+, were measured at day 1, day 7, day 14, day 21, and day 28 post-infection. Severe cases showed a significantly stronger increase than mild patients in levels of all cytokines (except IL-9) and all gene expression on day 1 of infection. Some cytokine levels dropped to levels comparable to mild cases at later time points. Further analysis identified IFNγ as a marker of severity throughout the disease course, while TGFβ1, IL-6, and IL-17 were markers of severity only at an early phase. Importantly, this study revealed a striking low IL-9 level and high IFNγ/IL-9 ratio in the plasma of patients who later died compared to mild and severe cases who recovered, suggesting that this could be an important biomarker for predicting the severity of COVID-19 and post-COVID-19 syndrome.

Silica-carrying particulate matter enhances Bjerkandera adusta-induced murine lung eosinophilia

Bjerkandera adusta (B. adusta) causes fungus-associated chronic cough. However, the inflammatory response is not yet fully understood. Recently, B. adusta was identified in Asian sand dust (ASD) aerosol. This study investigated the enhancing effects of ASD on B. adusta-induced lung inflammation. B. adusta was inactivated by formalin. ASD was heated to remove toxic organic substances. ICR mice were intratracheally instilled with saline, B. adusta 0.2 µg, or B. adusta 0.8 µg with or without heated ASD 0.1 mg (H-ASD), four times at 2-week intervals. Two in vitro experiments were conducted to investigate any enhancing effects using bone marrow-derived macrophages (BMDM) from Toll-like receptor (TLR) knockout mice and ICR mice. Co-exposure to H-ASD and B. adusta, especially at high doses, caused eosinophil infiltration, proliferation of goblet cells in the airway, and fibrous thickening of the subepithelial layer, and remarkable increases in expression of Th2 cytokines and eosinophil-related cytokine and chemokine expression in bronchoalveolar lavage fluid. In the in vitro study using BMDM from wild-type, TLR2-/-, and TLR4-/- mice, the TLR-signaling pathway for cytokine production caused by B. adusta was predominantly TLR2 rather than TLR4. H-ASD increased the expression of NF-κB and cytokine production by B. adusta in BMDM from ICR mice. The results suggest that co-exposure to H-ASD and B. adusta caused aggravated lung eosinophilia via remarkable increases of pro-inflammatory mediators. The aggravation of inflammation may be related, at least in part, to the activation of the TLR2-NF-κB signaling pathway in antigen presenting cells by H-ASD.

Early-shared Mycobacterium bovis bacillus Calmette-Guérin sub-strains induce Th1 cytokine production in vivo

Interleukin-12 is one of the cytokines that induce acquired immunity by progressing the differentiation of T cells. When antigens are presented by APCs, including macrophages and DCs, T cells are activated and produce the Th1 cytokines IL-2 and IFN-γ. We have previously reported greater IL-12 production from macrophages infected with early-shared BCG sub-strains (ex. BCG-Japan, -Sweden) than from those infected with late-shared BCG (ex. BCG-Pasteur and -Connaught) . In this study, we investigated the Th1 cytokine-inducing activity of splenocytes co-cultured with BCG-infected DCs. Early-shared BCG-infected DCs produced IL-12 and TNF-α⋅ Furthermore, when they were co-cultured with purified protein derivative-stimulated DCs, the splenocytes of mice immunized with BCG-Tokyo/Japan produced more Th1 cytokine than did those of mice immunized with BCG-Connaught. In conclusion, early-shared BCG sub-strains more strongly induce Th1 cytokine production in vivo. This study provides basic information to inform the selection of candidates for primary vaccination.

The antibody-based delivery of interleukin-12 to the tumor neovasculature eradicates murine models of cancer in combination with paclitaxel

PURPOSE

Interleukin-12 (IL12) is a potent proinflammatory cytokine with antitumor activity. Its heterodimeric nature makes it compatible with a large variety of different immunocytokine formats. Here we report the design, production, and characterization of a novel immunocytokine, based on the fusion of the F8 antibody (specific to the alternatively spliced EDA domain of fibronectin, a marker of tumor neovasculature) with IL12 (termed IL12-F8-F8).

EXPERIMENTAL DESIGN

We developed a novel immunocytokine based on the sequential fusion of interleukin-12 as a single polypeptide with two F8 antibodies in single-chain Fv (scFv) format. The fusion protein was characterized in vitro, and its targeting performance was assessed in vivo. The immunocytokine antitumor activity was studied as monotherapy as well as in combination therapies in three different murine tumor models. Moreover, depletion experiments and tumor analysis revealed a dominant role of natural killer cells for the mechanism of action.

RESULTS

IL12-F8-F8 can be produced in mammalian cells, yielding a product of good pharmaceutical quality, capable of selective localization on the tumor neovasculature in vivo, as judged by quantitative biodistribution analysis with radioiodinated protein preparations. The protein potently inhibited tumor growth in three different immunocompetent syngeneic models of cancer. The treatment was generally well tolerated. Moreover, the IL12-F8-F8 fusion protein could be produced both with murine IL12 (mIL12) and with human IL12 (hIL12).

CONCLUSIONS

The potent antitumor activity of mIL12-F8-F8, studied alone or in combination with paclitaxel in different tumor models, paves the way to the clinical development of the fully human immunocytokine.

The effects of interleukin (IL)-12 and IL-4 deficiency on worm development and granuloma formation in Schistosoma japonicum-infected mice

CD4(+) T-helper (Th) cell is widely recognized to be capable of influencing worm development and egg granuloma formation after schistosome infection. Interleukin (IL)-12 and IL-4 play key roles in regulation of Th cell differentiation. In the present study, we subcutaneously inoculated mice with hybridoma cells secreting monoclonal antibodies to neutralize IL-12 and IL-4 and explored the effects of IL-12 and IL-4 deficiency on the worm development and granuloma formation in mice infected with cercariae of Schistosoma japonicum. It was found that deficiency of host IL-12 and IL-4 supported normal parasite survival and fecundity. However, worm development (length and female fecundity) was significantly enhanced in anti-IL-12-treated mice. Mean length of worms in anti-IL-12-treated group was significantly greater than that of intact controls on day 28 after infection (females, 11.84 ± 1.20 mm vs. 9.45 ± 1.34; males, 9.35 ± 1.21 mm vs. 8.10 ± 0.85 mm, p < 0.05). Liver egg load per pair of worms (1,770.12 ± 470.67 vs. 806.08 ± 232.37, p < 0.05) and uterine egg load of ovigerous females (93.08 ± 27.85 vs. 46.05 ± 34.24, p < 0.05) in anti-IL-12-treated mice were significantly higher than those in intact control 28 days postinfection. But these effects diminished 42 days postinfection (p > 0.05). Granuloma size in anti-IL-12-treated mice was significantly larger than that in intact mice 42 days postinfection (398.3 ± 80.7 μm vs. 294.4 ± 72.2 μm, p < 0.05). Granuloma fibrosis dramatically intensified in anti-IL-12-treated mice but diminished in anti-IL-4-treated mice. The results suggest that IL-12 may play an impeditive role in the development of S. japonicum and in granuloma formation as well as fibrosis. IL-4 may promote granuloma formation but have no effect on worm development.

Heat-killed Trypanosoma cruzi induces acute cardiac damage and polyantigenic autoimmunity

Chagas heart disease, caused by the protozoan parasite Trypanosoma cruzi, is a potentially fatal cardiomyopathy often associated with cardiac autoimmunity. T. cruzi infection induces the development of autoimmunity to a number of antigens via molecular mimicry and other mechanisms, but the genesis and pathogenic potential of this autoimmune response has not been fully elucidated. To determine whether exposure to T. cruzi antigens alone in the absence of active infection is sufficient to induce autoimmunity, we immunized A/J mice with heat-killed T. cruzi (HKTC) emulsified in complete Freund's adjuvant, and compared the resulting immune response to that induced by infection with live T. cruzi. We found that HKTC immunization is capable of inducing acute cardiac damage, as evidenced by elevated serum cardiac troponin I, and that this damage is associated with the generation of polyantigenic humoral and cell-mediated autoimmunity with similar antigen specificity to that induced by infection with T. cruzi. However, while significant and preferential production of Th1 and Th17-associated cytokines, accompanied by myocarditis, develops in T. cruzi-infected mice, HKTC-immunized mice produce lower levels of these cytokines, do not develop Th1-skewed immunity, and lack tissue inflammation. These results demonstrate that exposure to parasite antigen alone is sufficient to induce autoimmunity and cardiac damage, yet additional immune factors, including a dominant Th1/Th17 immune response, are likely required to induce cardiac inflammation.

Anti-ribosomal P protein antibody induces Th1 responses by enhancing the production of IL-12 in activated monocytes

Autoantibodies to ribosomal P proteins (anti-P) are detected in 12-16% of patients with systemic lupus erythematosus (SLE), and have been found to be associated with some manifestations, including lupus psychosis, nephritis and hepatitis. We have recently disclosed that anti-P react with activated human peripheral blood monocytes, and enhance their production of tumor necrosis factor-α and interleukin (IL)-6. It is also possible that anti-P might regulate other monocyte functions, including the regulation of T helper (Th) responses. The current study was therefore undertaken to explore the effects of anti-P on the induction of Th1 responses. Peripheral blood mononuclear cells (PBMC) from healthy donors were cultured with affinity-purified anti-P or control IgG. Highly purified monocytes were cultured with interferon (IFN)-γ in the presence of anti-P or normal IgG. Anti-P significantly enhanced the production of IFN-γ by PBMC. Of note, anti-IL-12 monoclonal antibodies almost completely abrogated the anti-P-mediated upregulation of the IFN-γ production of PBMC. Accordingly, anti-P significantly enhanced the production of IL-12 by activated monocytes. These results indicate that anti-P induce Th1 responses by upregulating the production of IL-12 by activated monocytes. The data therefore suggest that anti-P play an important role in the pathogenesis of SLE through the promotion of Th1 responses.

Antigenic dietary protein guides maturation of the host immune system promoting resistance to Leishmania major infection in C57BL/6 mice

The immature immune system requires constant stimulation by foreign antigens during the early stages of life to develop properly and to create efficient immune responses against later infections. We have previously shown that intake of antigenic dietary protein is critical for inducing maturation of the immune system as well as for the development of T helper type 1 (Th1) immunity. In this study, we show that administration of an amino acid (aa)-based diet during the development of the immune system subsequently resulted in inefficient control of Leishmania major infection in adult C57BL/6 mice. Compared with mice fed a control protein-containing diet, adult aa-fed mice showed a decreased interferon (IFN)-gamma response to parasite antigens and insufficient production of nitric oxide (NO), which is crucial to parasite death. However, no deviation towards Th2-specific immunity to L. major was observed. Phenotypic analysis of antigen-presenting cells (APCs) from aa-fed mice revealed deficient levels of the costimulatory molecules CD40 and CD80, and low levels of interleukin (IL)-12 produced by peritoneal macrophages, revealing an early stage of maturation of these cells. APCs isolated from aa-fed mice were unable to stimulate a Th1 response in vitro. Both phenotypic features of T cells from aa-fed mice and their ability to produce a Th1 response in the presence of mature APCs were unaffected when compared with T cells from control mice. The results presented here support the notion that regulation of Th1 immunity to infection includes environmental factors such as dietary proteins, which provide a natural source of stimulation that contributes to the process of maturation of APCs.

Heat-treated Lactobacillus crispatus KT strains reduce allergic symptoms in mice

In the current study, we investigated the effects of heat-treated Lactobacillus crispatus KT strains on allergic response in mice. We found that the number of interferon (IFN)-gamma(+)CD4(+) cells was higher in C3H/HeN mouse spleen cultures incubated with L. crispatus KT strains than in those cultured with Lactobacillus JCM type cultures. The serum immunoglobulin E levels in NC/Nga mice that were administered KT strains were lower than those in the mice that were not given any bacterium. The ratio of spleen IFN-gamma(+)CD4(+)/interleukin-4(+)CD4(+) was highest in mice given L. crispatus KT-11. L. crispatus KT-11 also increased the expression of Toll-like receptor (TLR) 2, nucleotide-binding oligomerization domain (NOD) 1, and NOD2 in C3H/HeN mouse Peyer's patch cells. These results suggest that the L. crispatus KT-11 strain reduces allergic symptoms in NC/Nga mice via the adjustment of the type 1 helper T cell and type 2 helper T cell balance via TLR2, NOD1, and NOD2.

Counterregulation of Th2 immunity by interleukin 12 reduces host defenses against Strongyloides venezuelensis infection

The aim of this study was to investigate the role of interleukin 12 (IL-12) during Strongyloides venezuelensis infection. IL-12(-/-) and wild-type C57BL/6 mice were subcutaneously infected with 1500 larvae of S. venezuelensis. On days 7, 14, and 21 post-infection, we determined eosinophil and mononuclear cell numbers in the blood and broncoalveolar lavage fluid (BALF), Th2 cytokine secretion in the lung parenchyma, and serum antibody levels. The numbers of eggs in the feces and worm parasites in the duodena were also quantified. The eosinophil and mononuclear cell counts and the concentrations of IL-3, IL-5, IL-10, IL-13, and IgG1 and IgE antibodies increased significantly in infected IL-12(-/-) and wild-type mice as compared with uninfected controls. However, the number of eosinophils and mononuclear cells in the blood and BALF and the Th2 cytokine levels in the lungs of infected IL-12(-/-) mice were greater than in infected wild-type C57BL/6 mice. In addition, serum IgE and IgG1 levels were also significantly enhanced in the infected mice lacking IL-12. Meanwhile, parasite burden and fecal egg counts were significantly decreased in infected IL-12(-/-) mice. Together, our results showed that the absence of IL-12 upregulates the Th2 immune response, which is important for control of S. venezuelensis infection.

Regulation of T lymphocyte subsets

Patterns of cytokine secretion and functional differences distinguish T lymphocyte subsets. T lymphocyte subsets are also regulated differentially. Most established CD8+ lymphocyte clones secrete gamma-interferon (IFN-gamma) but not interleukin 2 (IL-2) or IL-4. Using murine T cells which express a transgenic, antigen-specific alpha/beta T cell receptor (TCR) specific for L(d) class I major histocompatibility complex antigen, we have found that CD8+ lymphocytes can be divided into functional subsets. Freshly isolated CD8+ T cells are not cytolytic, do not proliferate and do not proliferate and do not secrete cytokines. Stimulation of TCR alone does not induce cytokine secretion, but cells become responsive to exogenous IL-2 or IL-4. Stimulation of CD28 together with TCR induces secretion of IL-2 and IFN-gamma, and cells proliferate without exogenous cytokines. Proliferation is necessary for the development of cytolytic activity. If IL-4 is present during initial stimulation, IL-4 is secreted following restimulation. Upon stimulation, some IL-4-producing murine CD8+ T cell clones express CD40 ligand (CD40L), and they potentiate proliferation and immunoglobulin secretion by small resting B cells. Thus, the CD8+ T cell subsets T cytotoxic 1 (Tc1) and Tc2 are analogous to CD4+ T helper 1 (Th1) and Th2. IL-2 production by naive CD8+ cells requires co-stimulation. IL-4 production by CD8+ T cells requires the presence of IL-4 during initial stimulation. Some IL-4-producing CD8+ T cells express CD40L following TCR stimulation and provide help for B cells.

IL-13 prolongs allograft survival: Association with inhibition of macrophage cytokine activation

Th2 cytokines, especially IL-4 and IL-10, may facilitate transplant tolerance induction but the role of IL-13, another Th2 cytokine, is not known. This study examined the effects of rat recombinant IL-13 (rIL-13) on alloimmune responses. In vitro effects of rIL-13 were compared in mixed lymphocyte cultures (MLC) on rat lymphocytes cultured with PVG stimulator cells. DA rats grafted with fully allogeneic PVG neonatal heart grafts were treated with 40,000 units of rIL-13 for 10 days and graft survival monitored by ECG. Cytokine mRNA expression in the graft and lymphoid tissues was studied by RT-PCR and alloantibody levels assayed. rIL-13 had no effect on MLC, unlike rIL-4 which enhanced proliferation and induced Th2 and inhibited Th1 cytokines in MLC. rIL-13 inhibited IL-12p35, IL-12p40 and TNF-alpha mRNA induction in dendritic cell cultures. Treatment with rIL-13 prolonged fully allogeneic PVG neonatal heart graft survival to 18-21 (13-27) days (median (range)); compared to 12 (9-15) days in untreated normal rejection (p<0.05) and 14 (10-24) days in sham treated controls (p<0.05). RT-PCR studies on graft tissue identified reduced mRNA expression for the dendritic cell/macrophage molecules iNOS, TNF-alpha and IL-12 compared to normal rejection. rIL-13 treatment did not increase Th2 cytokines as compared to normal rejection, or the Th2 dependent IgG1 alloantibody response, while IL-4 did. These studies demonstrated that rIL-13 can prolong allograft survival associated with inhibition of IL-12, TNF-alpha and iNOS mRNA induction, and suggest IL-13 could modify graft rejection by inhibition of dendritic cell and/or macrophage function.

Inhibition of cellular immune responses to encapsulated porcine islet xenografts by simultaneous blockade of two different costimulatory pathways

BACKGROUND

Transplantation of human islets has been successful clinically. Since human islets are scarce, we are studying microencapsulated porcine islet xenografts in nonobese diabetic (NOD) mice. We have evaluated the cellular immune response in NOD mice with and without dual costimulatory blockade.

METHODS

Alginate-poly-L-lysine-encapsulated adult porcine islets were transplanted i.p. in untreated diabetic NODs and NODs treated with CTLA4-Ig to block CD28/B7 and with anti-CD154 mAb to inhibit CD40/CD40-ligand interactions. Groups of mice were sacrificed on subsequent days; microcapsules were evaluated by histology; peritoneal cells were analyzed by FACS; and peritoneal cytokines were quantified by ELISA. Controls included immunoincompetent NOD-Scids and diabetic NODs given sham surgery or empty microcapsules.

RESULTS

Within 20 days, encapsulated porcine islets induced accumulation of large numbers of macrophages, eosinophils, and significant numbers of CD4 and CD8 T cells at the graft site, and all grafts were rejected. During rejection, IFNgamma, IL-12 and IL-5 were significantly elevated over sham-operated controls, whereas IL-2, TNFalpha, IL-4, IL-6, IL-10, IL-1beta and TGFbeta were unchanged. Treatment with CTLA4-Ig and anti-CD154 prevented graft destruction in all animals during the 26 days of the experiment, dramatically inhibited recruitment of host inflammatory cells, and inhibited peritoneal IFNgamma and IL-5 concentrations while delaying IL-12 production.

CONCLUSIONS

When two different pathways of T cell costimulation were blocked, T cell-dependent inflammatory responses were inhibited, and survival of encapsulated islet xenografts was significantly prolonged. These findings suggest synergy between encapsulation of donor islets and simultaneous blockade of two host costimulatory pathways in prolonging xenoislet transplant survival.

CpG motifs are efficient adjuvants for DNA cancer vaccines

DNA vaccines can induce impressive specific cellular immune response (IR) when taking advantage of their recognition as pathogen-associated molecular patterns (PAMP) through Toll-like receptors (TLR) expressed on/in cells of the innate immune system. Among the many types of PAMP, immunostimulatory DNA, so-called CpG motifs, was shown to interact specifically with TLR9, which is expressed in plasmacytoid dendritic cells (pDC), a key regulatory cell for the activation of innate and adaptive IR. We now report that CpG motifs, when introduced into the backbone, are a useful adjuvant for plasmid-based DNA (pDNA) vaccines to induce melanoma antigen-specific protective T cell responses in the Cloudman M3/DBA/2 model. The CpG-enriched pDNA vaccine induced protection against subsequent challenge with melanoma cells at significantly higher levels than its parental unmodified vector. Preferential induction of an antigen-specific, protective T cell response could be demonstrated by (i) induction of antigen-dependent tumor cell protection, (ii) complete loss of protection by in vivo CD4+/CD8+T cell- but not NK cell-depletion, and (iii) the detection of antigen-specific T cell responses but not of relevant NK cell activity in vitro. These results demonstrate that employing PAMP in pDNA vaccines improves the induction of protective, antigen-specific, T cell-mediated IR.

Effects of deviating the Th2-response in murine mercury-induced autoimmunity towards a Th1-response

T-helper cells type 1 (Th1) and type 2 (Th2) play an important role in the pathogenesis of autoimmune diseases. In many Th1-dependent autoimmune models, treatment with recombinant interleukin-12 (rIL-12) accelerates the autoimmune response. Mercury-induced autoimmunity (HgIA) in mice is an H-2 regulated condition with antinucleolar antibodies targeting fibrillarin (ANoA), systemic immune-complex (IC) deposits and transient polyclonal B-cell activation (PBA). HgIA has many characteristics of a Th2 type of reaction, including a strong increase of IgE, but disease induction is critically dependent on the Th1 cytokine IFN-gamma. The aim of this study was to investigate if a strong deviation of the immune response in HgIA towards Th1 would aggravate HgIA. Injections of both rIL-12 and anti-IL-4 monoclonal antibody (alpha-IL-4) reduced the HgCl2-(Hg-)induced concentration of the Th2-dependent serum IgE and IgG1, but increased the Th1-dependent serum IgG2a. The IgG-ANoA developed earlier and attained a higher titre after combined treatment, and the ANoA titre of the IgG1 isotype decreased while the ANoA titre of the Th1-associated IgG2a, IgG2b and IgG3-ANoA isotypes increased. Treatment with rIL-12 alone increased the Hg-induced IgG2a and IgG3 ANoA titres, the PBA, and the IC deposits in renal and splenic vessel walls, while treatment with alpha-IL-4 + Hg inhibited renal but not splenic vessel wall IC deposits. We conclude that manipulating the cytokine status, by altering the Th1/Th2 balance, will influence autoimmune disease manifestations. This might be an important way of modulating human autoimmune diseases.

Immune response to hepatitis B vaccine in asthmatic children

Asthma is a disease that demonstrates chronic Th2 lymphocyte-mediated pulmonary inflammation. We hypothesized that cytokines produced by asthmatic lung inflammation bias the immune response to antigens administered systemically toward a Th2 response, as assessed by serum IgE antibody and lymphocyte-secreted IL-4 and IL-5. We also hypothesized that treatment of asthmatic children with local anti-inflammatory agents reduces this cytokine-mediated Th2 influence. We systemically immunized groups of asthmatic children (n=29) who were participating in a long-term, randomized, placebo-controlled clinical trial of inhaled anti-inflammatory therapy (Childhood Asthma Management Program) and nonasthmatic children (n=12) with hepatitis B (Hep B) antigen, and examined their antigen-specific antibody and lymphocyte cytokine secretion profiles. The asthmatic population demonstrated an increased amount of Th2-mediated serum IgE anti-Hep B antibody, as compared to nonasthmatic children; but comparable amounts of IgG1, IgG2, IgG3, IgA, and IgM anti-Hep B antibody and lymphocyte IFNgamma, IL4, and IL5. There was no significant difference of antibody isotype or cytokine production between asthmatic subjects receiving treatment with budesonide or nedocromil, as compared to placebo. In conclusion, there is a subtle bias in responses to systemic immunization in children with asthma, but anti-inflammatory therapy does not affect this bias. The findings support the concept that the Th2 bias may be largely genetic. Importantly, we confirmed that children with asthma, including even those on inhaled corticosteroids, responded to Hep B immunization as well as did nonasthmatic children with the major isotypes of anti-Hep B antibody, suggesting that vaccine protection against hepatitis B is not influenced by inhaled steroid therapy.

Regulatory effects of IL-12 and IL-18 on Onchocerca volvulus- and Entamoeba histolytica-specific cellular reactivity and cytokine profiles

In the present study, the cytokines interleukin (IL)-12 and IL-18 were evaluated for their capacity to modulate and to re-direct in vitro parasite antigen-specific cellular responsiveness in patients exposed to Onchocerca volvulus and Entamoeba histolytica infection. We found that IL-18 was highly capable of reducing parasite antigen-induced IL-10 production by PBMC. In contrast, addition or neutralization of IL-12, also in combination with IL-18 and the interferon-gamma-inducible chemokine IP-10 did not affect IL-10 production. Interestingly, the highest IL-10 levels were measured when IL-18 and IP-10 were both neutralized. Although having no effect on IL-10, IL-12 strongly promoted spontaneous and parasite antigen-driven IFN-gamma production by PBMC, whereas IL-18 was only moderately affecting IFN-gamma release by PBMC re-stimulated with E. histolytica- or O. volvulus-specific antigens. Both IL-12 and IL-18 diminished the cellular production of IL-13, and a synergistic effect was observed when the cytokines were combined. Likewise, neutralization of IL-12 enhanced Entamoeba and Onchocerca antigen-driven IL-13 production, but no further increase of IL-13 was observed, when anti-IL-12 and anti-IL-18 were used together. This study disclosed that IL-18 will significantly down-regulate parasite-specific IL-10 production, whereas IL-12 induced IFN-gamma and inhibited IL-13 production by PBMC from humans exposed to O. volvulus and E. histolytica. Such selective immune-regulatory capacity of IL-12 and IL-18 may comprise an important tool to re-direct polarized cytokine responses towards a balanced Th1/Th2 cytokine profile, which may prevent pathology and promote immunity against helminth and protozoan parasite infections.

Interleukin-12 and interleukin-2-induced invariant natural killer T-cell cytokine secretion and perforin expression independent of T-cell receptor activation

Human invariant natural killer (iNK) T cells expressing an invariant Valpha24-Jalpha15 T-cell receptor (TCR) are thought to be important regulators of autoimmunity and tumour surveillance. Two major subsets of iNK T cells, CD4+ or CD4- CD8- are known to exist, but the in vivo importance of CD4 expression is unclear. Since interleukin-12 (IL-12) is a key iNK T-cell-activating cytokine, the effect of IL-12 plus or minus the T-cell growth factor IL-2 on a large panel of CD4+ versus CD4- CD8- iNK T-cell clones was examined. Strikingly, IL-12 and IL-2 significantly activated iNK T cells to secrete IL-4, interferon-gamma and granulocyte-macrophage colony-stimulating factor, and up-regulated perforin expression in the absence of TCR stimulation. Furthermore, IL-2 and IL-12 treatment resulted in a preferential increase in apoptosis of CD4- CD8- clones. Thus, independent of TCR activation, IL-2 and IL-12 can directly activate iNK T cells and provide a selective advantage to the CD4+ iNK T-cell population.

Differential regulation of Th1 responses and CD154 expression in human CD4+ T cells by IFN-alpha

Like interleukin (IL)-12, interferon (IFN)-alpha has been shown to play an important role in inducing human Th1 responses. Recent studies have shown that human Th1 responses driven by IL-12 are associated with enhanced expression of CD154. The present study examined the effects of IFN-alpha on CD154 expression in human CD4+ T cells, with special attention to the relationship with Th1 responses. Highly purified CD4+ T cells from healthy donors were stimulated with immobilized anti-CD3 with or without IFN-alpha and IL-12 in the complete absence of accessory cells. IFN-alpha suppressed CD154 protein and mRNA expression in CD4+ T cells at the initial phase of activation with immobilized anti-CD3, but enhanced it in the subsequent maturation phase irrespective of the presence of IL-12. By contrast, IFN-alpha by itself did not enhance IFN-gamma production or mRNA expression in CD4+ T cells in the absence of IL-12 even in the presence of stimulation with anti-CD28, but enhanced it in the presence of IL-12. Accordingly, IFN-alpha enhanced IL-12Rbeta2 mRNA expression in anti-CD3-stimulated CD4+ T cells. Neither IFN-alpha nor IL-12 influenced the stability of CD154 mRNA in anti-CD3-activated CD4+ T cells. These results indicate that IFN-alpha by itself enhances CD154 expression in CD4+ T cells independently of the induction of IFN-gamma mRNA expression. The data also suggest that the optimal induction of human Th1 responses by IFN-alpha might require the presence of IL-12 and that the induction of Th1 responses and CD154 expression in human CD4+ T cells might be regulated through different mechanisms.

Cytokine memory of T helper lymphocytes

Memory is one of the key features of the adaptive immune system. Specific T and B lymphocytes are primed for a particular antigen and upon challenge with it will react faster than naive lymphocytes. They also memorize the expression of key effector molecules, in particular cytokines, which determine the type and scale of an immune reaction. While in primary activations differential expression of cytokine genes is dependent on antigen-receptor signaling and differentiation signals, in later activations the expression is triggered by antigen-receptor signaling and dependent on the cytokine memory. The molecular basis of the cytokine memory implies differential expression of transcription factors and epigenetic modifications of cytokine genes and gene loci. GATA-3 for Th2 and T-bet for Th1 cells expressing interleukin-4 or interferon-gamma, respectively, are prime candidates for key transcription factors of cytokine memory. The essential role of epigenetic modifications is suggested by the requirement of DNA synthesis for the establishment of a cytokine memory in Th lymphocytes. At present the molecular link between transcription factors and epigenetic modifications of cytokine genes in the establishment and maintenance of cytokine memory is not clear. The initial cytokine memory is not stable against adverse differentiation signals, while in repeatedly stimulated lymphocytes it is stabilized by a variety of mechanisms.

Induction of specific immune responses by polycation-based vaccines

The s.c injection of tumor Ag-derived, MHC class I-binding peptides together with cationic poly-amino acids (e.g., poly-L-arginine; pR) has been shown to protect animals against a challenge with tumor cells expressing the respective peptide(s). Given our only restricted knowledge about immunogenic tumor-associated peptides, we sought to determine whether this pR-based vaccination protocol would also induce protective cancer immunity if large proteins were used instead of peptide epitopes. We found that the intracutaneous administration of the model Ag beta-galactosidase (beta-gal) together with pR (referred to as pR-based protein vaccine; pR-PV) was significantly more potent in protecting mice against the growth of beta-gal-expressing RENCA cells than the protein alone. Coadministration of pR enhanced both the beta-gal-induced specific humoral and CD8 response. The protective effect required CD8(+), but neither CD4(+) T lymphocytes nor beta-gal-specific Abs. beta-Gal priming of protective CD8(+) T lymphocytes was found to be CD4(+) T cell-independent, to take place within the draining lymph nodes, and to be accomplished by day 5 after vaccination. Ablation of the injection sites as early as 1.5 h after pR-PV administration still led to protection in a large proportion of the animals, indicating that certain protein Ags administered intradermally in the context of polycations are quickly transported to the draining nodes, where they induce molecular and cellular events resulting in the helper-independent priming and expansion of Tc1 cells. However, optimal protection required the prolonged presence of the injection site, suggesting that pR-PV injection facilitates the formation of a cutaneous depot of Ag-charged cells capable of migration and T cell activation.

IL-12-independent IFN-gamma production by T cells in experimental Chagas' disease is mediated by IL-18

IL-12p35-deficient (IL-12p35(-/-)) mice were highly susceptible to Trypanosoma cruzi infection and succumbed during acute infection, demonstrating the crucial importance of endogenous IL-12 in resistance to experimental Chagas' disease. Delayed immune responses were observed in mutant mice, although comparable IFN-gamma and TNF-alpha blood levels as in wild-type mice were detected 2 wk postinfection. In vivo and in vitro analysis demonstrated that T cells, but not NK cells, were recruited to infected organs. Analysis of mice double deficient in the recombinase-activating gene 2 (RAG2) and IL-12p35, as well as studies involving T cell depletion, identified CD4(+) T cells as the cellular source for IL-12-independent IFN-gamma production. IL-18 was induced in IL-12p35(-/-) mice and was responsible for IFN-gamma production, as demonstrated by in vivo IL-18 neutralization studies. In conclusion, evidence is presented for an IL-12-independent IFN-gamma production in experimental Chagas' disease that is T cell and IL-18 dependent.

Filarial antigens impair the function of human dendritic cells during differentiation

The antigen-specific T-cell unresponsiveness seen in lymphatic filariasis is mediated, in part, by diminished antigen-presenting cell function and is most specific for microfilariae (MF), the parasite stage found in large numbers in the peripheral circulation. We investigated the effect of MF antigen (MFAg) on dendritic cells (DC) in both their differentiation process from monocyte precursors and also after they have developed into DC. When MFAg was added to cultures of monocytes during their differentiation process to immature DC, the production of interleukin 12 (IL-12) p40, p70 protein, and IL-10 was significantly (P < 0.03) inhibited in response to Staphylococcus aureus Cowan (SAC) and SAC-gamma interferon (IFN-gamma) (60% to 80% inhibition). IL-10 was also inhibited (P = 0.04) in response to CD40 ligand-IFN-gamma. Moreover, MFAg inhibited the mRNA expression of IL-12 p40 and IL-10 as assessed by RNA protection assays. This effect was antigen specific, as another parasite antigen (soluble Toxoplasma gondii antigen) did not inhibit the production of these cytokines. This effect was also not a result of diminished cell viability nor of an alteration in surface expression of most costimulatory surface molecules, including major histocompatibility complex class I and class II. In contrast to exposure throughout the differentiation process, MFAg added to immature DC had no effect on DC cytokine expression. Although MF-differentiated DC were capable of inducing an allogeneic mixed lymphocyte reaction, they did so to a significantly lesser degree than DC without antigen exposure. These data collectively suggest that once DC are differentiated from their precursor cells, they become resistant to changes by MFAg.

Distinct cytokine regulation by cholera toxin and type II heat-labile toxins involves differential regulation of CD40 ligand on CD4(+) T cells

Cholera toxin (CT) and the type II heat-labile enterotoxins (HLT) LT-IIa and LT-IIb act as potent systemic and mucosal adjuvants and induce distinct T-helper (Th)-cell cytokine profiles. In the present study, CT and the type II HLT were found to differentially affect cytokine production by anti-CD3-stimulated human peripheral blood mononuclear cells (PBMC), and the cellular mechanisms responsible were investigated. CT suppressed interleukin-2 (IL-2), tumor necrosis factor alpha (TNF-alpha), and IL-12 production by PBMC cultures more than either LT-IIa or LT-IIb. CT but not LT-IIa or LT-IIb reduced the expression of CD4(+) T-cell surface activation markers (CD25 and CD69) and subsequent proliferative responses of anti-CD3-stimulated T cells. CT but not LT-IIa or LT-IIb significantly reduced the expression of CD40 ligand (CD40L) on CD4(+) T cells. In a coculture system, CT-treated CD4(+) T cells induced significantly less TNF-alpha and IL-12 p70 production by both autologous monocytes and monocyte-derived dendritic cells than either LT-IIa- or LT-IIb-treated CD4(+) T cells. These findings demonstrate that CT, LT-IIa, and LT-IIb differentially affect CD40-CD40L interactions between antigen-presenting cells and T cells and help explain the distinct cytokine profiles observed with type I and type II HLT when used as mucosal adjuvants.

Liver-derived DEC205+B220+CD19- dendritic cells regulate T cell responses

Leukocytes resident in the liver may play a role in immune responses. We describe a cell population propagated from mouse liver nonparenchymal cells in IL-3 and anti-CD40 mAb that exhibits a distinct surface immunophenotype and function in directing differentiation of naive allogeneic T cells. After culture, such cells are DEC-205(bright)B220+CD11c-CD19-, and negative for T (CD3, CD4, CD8alpha), NK (NK 1.1) cell markers, and myeloid Ags (CD11b, CD13, CD14). These liver-derived DEC205+B220+ CD19- cells have a morphology and migratory capacity similar to dendritic cells. Interestingly, they possess Ig gene rearrangements, but lack Ig molecule expression on the cell surface. They induce low thymidine uptake of allogeneic T cells in MLR due to extensive apoptosis of activated T cells. T cell proliferation is restored by addition of the common caspase inhibitor peptide, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk). T cells stimulated by liver-derived DEC205+B220+D19- cells release both IL-10 and IFN-gamma, small amounts of TGF-beta, and no IL-2 or IL-4, a cytokine profile resembling T regulatory type 1 cells. Expression of IL-10 and IFN-gamma, but not bioactive IL-12 in liver DEC205+B220+CD19- cells was demonstrated by RNase protection assay. In vivo administration of liver DEC205+B220+CD19- cells significantly prolonged the survival of vascularized cardiac allografts in an alloantigen-specific manner.

A filarial nematode-secreted product signals dendritic cells to acquire a phenotype that drives development of Th2 cells

Although exogeneous "danger" signals such as LPS can activate APC to produce a Th1 response, the nature of events initiating a Th2 response is controversial. We now show that pathogen-derived products have the capacity to induce bone marrow-derived dendritic cell cultures to acquire a phenotype that promotes the differentiation of naive CD4+ T cells toward either a Th1 or Th2 phenotype. Thus, LPS-matured dendritic cells (DC1) promote a Th1 response (increased generation of IFN-gamma and reduced production of IL-4) by Ag-stimulated CD4+ T cells from the DO.11.10 transgenic mouse expressing a TCR specific for an OVA peptide (OVA323-339). In contrast, a phosphorylcholine-containing glycoprotein, ES-62, secreted by the filarial nematode, Acanthocheilonema viteae, which generates a Th2 Ab response in vivo, is found to induce the maturation of dendritic cells (DC2) with the capacity to induce Th2 responses (increased IL-4 and decreased IFN-gamma). In addition, we show that the switch to either Th1 or Th2 responses is not effected by differential regulation through CD80 or CD86 and that a Th2 response is achieved in the presence of IL-12.

In activated mast cells, IL-1 up-regulates the production of several Th2-related cytokines including IL-9

Mast cells can play detrimental roles in the pathophysiology and mortality observed in anaphylaxis and other Th2-dominated allergic diseases. In contrast, these cells contribute to protective host defense mechanisms against parasitic worm infections. After IgE/Ag activation, mast cells can produce multiple cytokines that may enhance allergic inflammations, while a similar panel of Th2-related cytokines may support immunological strategies against parasites. Here we report that in primary mouse bone marrow-derived mast cells activated by ionomycin or IgE/Ag, the proinflammatory mediator IL-1 (alpha or beta) up-regulated production of IL-3, IL-5, IL-6, and IL-9 as well as TNF, i.e., cytokines implicated in many inflammatory processes including those associated with allergies and helminthic infections. IL-1 did not induce significant cytokine release in the absence of ionomycin or IgE/Ag, suggesting that Ca-dependent signaling was required. IL-1-mediated enhancement of cytokine expression was confirmed at the mRNA level by Northern blot and/or RT-PCR analysis. Our study reveals a role for IL-1 in the up-regulation of multiple mast cell-derived cytokines. Moreover, we identify mast cells as a novel source of IL-9. These results are of particular importance in the light of recent reports that strongly support a central role of IL-9 in allergic lung inflammation and in host defense against worm infections.

Progressive development of a Th1-type hepatic cytokine profile in rats with experimental cholangitis

Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are presumed autoimmune chronic cholestatic liver diseases characterized by cholangitis and progressive loss of bile ducts. Cytokines have been postulated to be involved in the progression of these diseases, but their role is poorly defined. Our objectives were to characterize a rat model of cholangitis and to determine Type 1/Type 2 (Th1/Th2) cytokine profile shifts in this model. Cholangitis was induced in Sprague-Dawley rats (200 to 225 g) by low-dose oral administration of the biliary toxin alpha-naphthylisothiocyanate (ANIT) (1 g/kg powdered rat chow ad libitum) for 4, 7, and 14 days. Cholestasis was observed in ANIT-treated animals. Liver histology of ANIT-treated rats showed hepatic inflammation centered on damaged bile ducts, significant bile duct proliferation, and progressive fibrosis. Immunohistochemistry showed enhanced staining of hepatic major histocompatibility complex (MHC) II, CD4, and CD8 in portal areas of ANIT-treated animals. In addition, the hepatic cytokine profile became increasingly Th1 in nature with progressive ANIT treatment. In summary, experimental cholangitis biochemically and histologically mimics human chronic cholangitis and furthermore, is associated with a progressive shift to a more Th1-dominant hepatic cytokine profile. Therefore, this model may be useful for examining the role of cytokines in the progression of chronic cholangitic diseases.

Experimental hypersensitivity pneumonitis: influence of Th2 bias

Cultured murine CD4+ cells from Saccharopolyspora rectivirgula sensitized C3H/HeJ (Th1 bias) donors can adoptively transfer murine experimental hypersensitivity pneumonitis (EHP). We sensitized BALB/c mice (Th2 bias) with S. rectivirgula, obtained spleen and lung associated lymph node (LALN) cells, cultured the cells with specific antigen, and attempted adoptive transfer of EHP. We also treated both C3H/HeJ and BALB/c donor mice with IL4 and anti-IFNgamma before exposure to S. rectivirgula and then cultured cells from both spleen and LALN before attempted transfer of EHP. We found that cultured spleen and lung associated lymph node cells can adoptively transfer EHP in both C3H/HeJ and BALB/c mice as demonstrated by infiltration of the recipient lungs with CD4+ lymphocytes. Treatment of both mouse strains with IL4 and anti-IFNgamma did not change the ability of cultured cells to adoptively transfer EHP. We conclude that EHP induced by S. rectivirgula can occur in animals with either a Th1 or a Th2 bias and is not altered by treatment with IL4 and anti-IFNgamma. This suggests that attributes of the antigen and not genetic background or cytokine environment at the site of initial sensitization determines the results of exposure to S. rectivirgula.

Proteoglycan (Aggrecan)-Induced Arthritis in BALB/c Mice Is a Th1-Type Disease Regulated by Th2 Cytokines

In animal models of arthritis induced with Ags or infectious agents, disease severity correlates with a dominant Th1-type response characterized by a higher ratio of IFN-γ to IL-4. Analysis of BALB/c mice revealed a genetic predisposition toward developing CD4+ Th2-type responses. The bias toward an IL-4-dominant response in BALB/c mice protects mice from severe Lyme-induced arthritis and spontaneous autoimmune disease. Since BALB/c mice immunized with proteoglycan develop severe arthritis, we were interested in testing whether arthritis is associated with a Th2-type response and thus is different from other arthritic models. BALB/c mice immunized with proteoglycan generated a higher ratio of IFN-γ to IL-4 that peaks at the onset of arthritis. We investigated whether when Th1 cells were dominant, disease outcome could be modified with pharmacological amounts of Th2 cytokines. Treatment with IL-4 prevented disease and induced a switch from a Th1-type to a Th2-type response. Proinflammatory cytokine mRNA transcripts were reduced in joints of cytokine-treated mice. Th2 cytokine therapy at the time of maximum joint inflammation also suppressed symptoms of disease. Despite the predisposition of BALB/c mice to a Th2-type response, proteoglycan-induced arthritis is a Th1-type disease. The effectiveness of IL-4 treatment was particularly striking because in other models of arthritis, treatment in a similar manner with IL-4 was not sufficient to inhibit arthritis. The effective control of arthritis and the switch from a Th1 to Th2 response suggest that levels of endogenous IL-4 in BALB/c mice may increase their responsiveness to Th2 cytokine therapy.

Expression of Th2 cytokines and the stable Th2 marker ST2L in the absence of IL-4 during Leishmania major infection

In this study we characterized Th2 responses in the absence of IL-4. We show that ST2L, a stable Th2 marker, is expressed at similar levels in Leishmania major-infected IL-4-deficient (IL-4(-/-)) and wild-type BALB/c (IL-4(+/+)) mice. Th2 cytokines are secreted by in vivo differentiated lymphocytes in response to specific activation in the absence of IL-4. Although IL-13 is produced, its neutralization did not alter the outcome of infection. Thus, we demonstrate that Th2 differentiation as assessed by the expression of ST2L and the production of Th2 cytokines can occur in vivo in the absence of IL-4.

Human CD4+ T cell differentiation and effector function: implications for autoimmunity

Human CD4+ memory T cells progress through stages of postthymic differentiation that have been characterized by distinct phenotypes. We have investigated the factors regulating cytokine production, and the correlation between phenotype and effector function in normal and autoimmune individuals. These studies suggest that antigen-induced proliferation in the periphery drives CD4+ T cells through successive stages of differentiation that culminate in optimal effector function and resistance to external modulatory influences. Moreover, these studies support the concept that in autoimmune individuals, the chronic accumulation of differentiated proinflammatory T cells perpetuate the inflammatory response resulting in aggressive disease.

Cure of progressive murine leishmaniasis: interleukin 4 dominance is abolished by transient CD4(+) T cell depletion and T helper cell type 1-selective cytokine therapy

Progressive infection with Leishmania major in susceptible BALB/c mice is mediated by interleukin (IL)-4-producing T helper cell type 2 (Th2) CD4(+) T cells that, once established, become resistant to Th1-deviating therapies with recombinant (r)IL-12 and/or neutralizing anti-IL-4 antibodies. We sought to restore protective immunity in advanced leishmaniasis by depletion of Th2-biased CD4(+) populations and by cytokine-directed reconstitution of Th1 cellular responses during lymphocyte recovery. Treatment with cytolytic GK1.5 anti-CD4 mAb alone did not reverse disease in 3 wk-infected BALB/c mice, but GK1.5 combined with anti-IL-4 antibody and intralesional rIL-12 cured cutaneous lesions in 80% of mice and established a Th1-polarized cytokine response to L. major antigen protective against reinfection. The curative effects of GK1.5 were not replaced by cytotoxic anti-CD8 monoclonal antibody 2.43 or nondepleting anti-CD4 mAb YTS177, confirming that depletion of CD4(+) cells was specific and essential for therapeutic effect. Finally, combined CD4(+) depletion and IL-4 neutralization were curative, indicating that neither increased parasite burden nor altered accessory cell function independently biased towards Th2 reconstitution in advanced leishmaniasis. Advanced leishmaniasis can be cured by T cell depletion and cytokine-directed recovery of Th1 cellular responses, suggesting novel interventions for other immune-mediated diseases and identifying distinct roles for CD4(+) T cell and non-T cell in the maintenance of Th2 and Th1 phenotypes.

Therapeutic Protective Effects of IL-12 Combined with Soluble IL-4 Receptor Against Established Infections of Herpes Simplex Virus Type 1 in Thermally Injured Mice

The effect of combination therapy between IL-12 and soluble IL-4R (sIL-4R) on the established infection of HSV-1 in thermally injured mice (TI mice) was investigated. All of the TI mice infected with lethal amounts of HSV-1 died when IL-12 was given therapeutically at a dose of 500 U/mouse. However, 80% of these mice treated prophylactically with IL-12 survived compared with 0% survival of the same mice treated with saline. The therapeutic administration of IL-12 to TI mice currently infected with HSV-1 caused an 80% survival of these mice when the treatment was combined with sIL-4R. Although IL-12 did not stimulate IFN-γ production in cultures of splenic T cells from TI mice, IFN-γ was produced by stimulation with IL-12 when the producer cells were prepared from TI mice that had been treated previously with sIL-4R. After stimulation with anti-CD3 mAb, splenic T cells from TI mice with the established infection of HSV-1 produced IL-4 into their culture fluids. However, IL-4 was not produced by splenic T cells that were prepared from the same infected mice treated with IL-12 and sIL-4R in combination. The results obtained herein indicate that the efficacies of the combination therapy against the established infection of HSV-1 may result from the IFN-γ production stimulated by IL-12 in TI mice that are treated with sIL-4R for reducing burn-associated type 2 T cell responses.

IL-12, IFN-γ, and T Cell Proliferation to Measles in Immunized Infants

Measles infection in infants is associated with severe complications, and secondary infections are attributed to generalized immunosuppression. Measles binding to its monocyte receptor down-regulates IL-12 which is expected to diminish Th1-like cytokine responses, including IFN-γ. Whether young infants can be immunized effectively against measles is an important public health issue. We evaluated Ag-specific IL-12, IFN-γ, and T cell responses of infants at 6 (n = 60), 9 (n = 46), or 12 mo (n = 56) of age and 29 vaccinated adults. IL-12 and IFN-γ release by PBMC stimulated with measles Ag increased significantly after measles immunization in infants. IL-12 and IFN-γ concentrations were equivalent in younger and older infants, but IL-12 concentrations were significantly lower in infants than in adults (p = 0.04). IL-12 production by monocytes was down-regulated by measles; the addition of recombinant human IL-12 enhanced IFN-γ production by PBMC stimulated with measles Ag, but infant T cells released significantly less IFN-γ than adult T cells under this condition. Of particular interest, the presence of passive Abs to measles had no effect on the specific T cell proliferation or IFN-γ production after measles stimulation. Cellular immunity to measles infection and vaccination may be limited in infants compared with adults as a result of less effective IFN-γ and IL-12 production in response to measles Ags. These effects were not exaggerated in younger infants compared with effects in infants who were immunized at 12 mo. In summary, infant T cells were primed with measles Ag despite the presence of passive Abs, but their adaptive immune responses were limited compared with those of adults.

Alternative polyadenylation events contribute to the induction of NF-ATc in effector T cells

The transcription factor NF-ATc is synthesized in three prominent isoforms. These differ in the length of their C terminal peptides and mode of synthesis. Due to a switch from the use of a 3' polyA site to a more proximal polyA site, NF-ATc expression switches from the synthesis of the two longer isoforms in naive T cells to that of short isoform A in T effector cells. The relative low binding affinity of cleavage stimulation factor CstF-64 to the proximal polyA site seems to contribute to its neglect in naive T cells. These alternative polyadenylation events ensure the rapid accumulation of high concentrations of NF-ATc necessary to exceed critical threshold levels of NF-ATc for gene induction in effector T cells.

Cytokines in parasitic diseases: the example of cutaneous leishmaniasis

The essential role of cytokines in parasitic diseases has been emphasised since the in vivo description of the importance of T helper 1 (Th1) and T helper 2 (Th2) CD4+ T cell responses in resistance and susceptibility to infection with L. major in mice. Th1 cells produced IL-2, IFN-gamma and Lymphotoxin T (LT) and Th2 cells produce IL-4, IL-5 and IL-13. In this model of infection the correlation between on the one hand resistance to infection and the development of a Th1 response and on the other hand susceptibility and Th2 cell development allowed the identification of the mechanisms directing the differentiation of CD4+ T cell precursors towards either Th1 type or Th2 type responses. Cytokines are the crucial inducer of functional CD4+ T cell subset differentiation during infection with L. major. IL-12 and IFN-gamma direct the differentiation of Th1 response and IL-4 of a Th2 response. In susceptible mice, careful analysis of IL-4 production during the first days of infection has shown that the IL-4 produced as a result of a very early burst of IL-4 mRNA expression (16 hours) plays a essential role in the maturation of a Th2 CD4+ T cell response by rendering the CD4+ T cell precursors unresponsive to IL-12. Activation of a restricted population of CD4+ T cells expressing the V beta 4 V alpha 8 TCR heterodimer after recognition of a single antigen, the LACK (Leishmania Activated c Kinase) antigen, resulted in this rapid production of IL-4 required for the subsequent CD4+ T cell differentiation. Thus, tolerization of these cells might contribute a strategy for preventing infection with L. major.

Interleukin 12 protects from a T helper type 1-mediated autoimmune disease, experimental autoimmune uveitis, through a mechanism involving interferon gamma, nitric oxide, and apoptosis

Pathogenic effector T cells in experimental autoimmune uveitis (EAU) are T helper type 1-like, and interleukin (IL)-12 is required for their generation and function. Therefore, we expected that IL-12 administration would have disease-enhancing effects. Mice were immunized with a uveitogenic regimen of the retinal antigen interphotoreceptor retinoid-binding protein, treated with IL-12 (100 ng/d for 5 d), and EAU was assessed by histopathology. Unexpectedly, IL-12 treatment failed to enhance EAU in resistant strains and downregulated disease in susceptible strains. Only treatment during the first, but not during the second, week after immunization was consistently protective. High levels of interferon gamma (IFN-gamma) were present in the serum during IL-12 treatment, but subsequent antigen-specific IFN-gamma production in protected mice was diminished, as were IL-5 production, lymph node cell proliferation, and serum antibody levels. Treated mice had fewer cells and evidence of enhanced apoptosis in the draining lymph nodes. Unlike wild-type mice, IFN-gamma-deficient, inducible nitric oxide synthase (iNOS)-deficient, and Bcl-2(lck) transgenic mice were poorly protected by IL-12, whereas IL-10-deficient mice were protected. We conclude that administration of IL-12 aborts disease by curtailing development of uveitogenic effector T cells. The data are compatible with the interpretation that IL-12 induces systemic hyperinduction of IFN-gamma, causing activation of iNOS and production of NO, which mediates protection at least in part by triggering Bcl-2 regulated apoptotic deletion of the antigen-specific T cells as they are being primed.

Use of Intranasal IL-12 to Target Predominantly Th1 Responses to Nasal and Th2 Responses to Oral Vaccines Given with Cholera Toxin

We have investigated the effects of IL-12 and cholera toxin (CT) on the immune response to tetanus toxoid (TT) given by intranasal or oral routes. CT inhibited IL-12-induced IFN-γ secretion both in vivo and in vitro. Intranasal administration of IL-12 to mice nasally immunized with the combined vaccine of TT and CT resulted in increased TT-specific IgG2a and IgG3 Abs, while IgG1 and IgE Ab responses were markedly reduced. This shift of the CT-induced immune response toward Th1 type was associated with TT-specific CD4+ T cells secreting IFN-γ and reduced levels of Th2-type cytokines (i.e., IL-4, IL-5, IL-6, and IL-10). In contrast, intranasal IL-12 enhanced the CT-induced serum IgG1 and IgE Ab responses in mice given the combined vaccine orally. IFN-γ secretion by TT-specific CD4+ T cells was also enhanced; however, Th2-type cytokine responses were predominant. Mucosal secretory IgA responses to oral or nasal vaccines were not affected by intranasal IL-12. Thus, intranasal IL-12 delivery influences Th cell subset development in mucosal inductive sites that are dependent on the route of vaccine delivery.

Presence or Absence of TGF-β Determines IL-4-Induced Generation of Type 1 or Type 2 CD8 T Cell Subsets

CD8+ T cells often differentiate into highly cytotoxic cells, secreting a Th1-like or type 1 cytokine pattern characterized by the production of IFN-γ. However, cytotoxic, and in some reports, noncytotoxic, type 2 cells that secrete IL-4, IL-5, or IL-10 instead of IFN-γ, can be generated when CD8+ T cells are primed in the presence of IL-4. Here, we show that IL-4 can also generate typical CD8 type 1 responses. Indeed, while presence of TGF-β biases the development of CD8 T cells that, then, produce little cytolytic activity and IFN-γ, addition of IL-4 results in the recovery of cytotoxicity and IFN-γ production. The cooperative effects of TGF-β and IL-4 imply dual functions, not only for IL-4, but also for TGF-β. Indeed, depending on the presence or absence of IL-4, TGF-β either inhibits or induces the generation of type 1 CD8+ T cells. Physiologically, the ratio of local IL-4/TGF-β concentration may therefore be a critical element in determining the outcome of T cell responses to pathogen and autoantigens. It allows CD8 T cells to switch from an immunotolerant state in the presence of only TGF-β or IL-4, to an immunocompetent proinflammatory type 1 state in the absence or presence of both cytokines.

IL-4 in Combination with TGF-β Favors an Alternative Pathway of Th1 Development Independent of IL-12

IL-4 was found to be the essential differentiation factor for Th2 cells and simultaneously to be a potent inhibitor of Th1 development that is induced by IFN-γ and IL-12. Furthermore, it was demonstrated that TGF-β can also inhibit Th1 development. In this work, we demonstrate that polyclonal activation of Mel-14highCD4+ T cells by immobilized anti-αβTCR mAb together with a mixture of IL-4 and TGF-β can lead to the development of both Th1 and Th2 cells, depending on the concentration of these cytokines. Additional experiments revealed that Th1 induction by a combination of IL-4 and TGF-β depends on the presence of endogenous IFN-γ, and that this alternative Th1 development is further enhanced by IL-12, but is not dependent on this cytokine. Moreover, naive OVA323–339-specific Th cells that were stimulated by APCs and OVA323–339 peptide differentiated toward Th1 cells after priming in the presence of IL-4 in combination with TGF-β. Hence, this finding confirmed the results obtained by polyclonal activation of naive CD4+ Th cells and implicates that this alternative Th1 development may also occur in vivo under the influence of TGF-β and IL-4 independently of the Th1-promoting effect of IL-12.

Commitment of Individual Th1-Like Lymphocytes to Expression of IFN-γ Versus IL-4 and IL-10: Selective Induction of IL-10 by Sequential Stimulation of Naive Th Cells with IL-12 and IL-4

Commitment of Th lymphocytes to the Th1 phenotype, as characterized by the expression of the major proinflammatory cytokine IFN-γ, may be critically involved in the establishment of chronic inflammation and inflammatory autoimmune disease. To date, it has been shown that in IL-12-stimulated murine Th cell lines containing a major fraction of Th1 cells, Th2 cells can be induced by IL-4 until about 2 wk after initial activation, but not later. Here we analyze, based on the magnetic isolation of viable Th1 cells according to their specific expression of IFN-γ, the cytokine commitment of individual Th1 cells. After activation of naive Th cells with Ag and IL-12 for up to 5 wk, isolated IFN-γ-producing cells were restimulated with Ag and IL-4. Within the first 3 to 4 wk of IL-12 stimulation, some IFN-γ+ cells stopped expression of IFN-γ when restimulated with IL-4. However, within only 1 to 2 wk of IL-12 stimulation, few IFN-γ+ cells could be converted to produce IL-4. Others continued to express IFN-γ and thus were already committed to a proinflammatory, Th1-like phenotype. Surprisingly, within 3 wk of IL-12 stimulation, many of the IFN-γ-producing cells responded to IL-4 restimulation by expression of IL-10, but neither IFN-γ nor IL-4, i.e., by conversion to a suppressive, anti-inflammatory phenotype.

Maturation of human neonatal CD4+ and CD8+ T lymphocytes into Th1/Th2 effectors

The increased susceptibility of neonates to infections has been ascribed to the immaturity of their immune system. More particularly, T cell-dependent responses were shown to be biased towards a Th2 phenotype. Our studies on the in vitro maturation of umbilical cord blood T cells suggest that the Th2 bias of neonatal response cannot be simply ascribed to intrinsic properties of neonatal T cells. Phenotypically, neonatal CD4+ T cells are more immature than their adult CD45RO-/RA+ naive counterparts and they contain a subset (10-20%) of CD45RO-/RA+ CD31- cells which is very low in adults and displays some unique functional features. The activation and maturation of neonatal CD4+ T cells is particularly dependent upon the strength of CD28-mediated cosignal which dictates not only the cytokine profile released upon primary activation but also the response to IL-12. Activation of adult as well as neonatal CD4+ T cells in the context of low CD28 costimulation yields to the production of low levels of only one cytokine, i.e. IL-2. In contrast, strong CD28 costimulation supports the production of high levels of type 1 (IL-2, IFN gamma and TNF beta) and low levels of type 2 (IL-4 and IL-13) cytokines by neonatal T cells. The low levels of naive T cell-derived IL-4 are sufficient to support their development into high IL-4/IL-5 producers by an autocrine pathway. The ability of IL-12 to prime neonatal CD4+ T cells for increased production of IL-4 (in addition to IFN gamma) is observed only when CD28 cosignal is minimal. Under optimal activation conditions (i.e. with anti-CD3/B7.1 or allogenic dendritic cells) the response and the maturation of neonatal and adult naive T cells are similar. Thus the Th2 bias of neonatal immune response cannot be simply ascribed to obvious intrinsic T cell defect but rather to particular conditions of Ag presentation at priming. Unlike CD4+ T cells, neonatal CD8+ T cells strictly require exogenous IL-4 to develop into IL-4/IL-5 producers. Most importantly, anti-CD3/B7-activated neonatal CD8 T cells coexpress CD4 as well as CCR5 and CXCR4 and are susceptible to HIV-1 infection in vitro.

Endogenous IL-12 Is Required for Induction and Expression of Experimental Autoimmune Uveitis

Experimental autoimmune uveitis (EAU) has been associated with a Th1 response. However, in IFN-γ-deficient mice, EAU develops in the context of an effector response having Th2-like elements, and administration of IL-12 to mice immunized for EAU induction can be protective. We, therefore, investigated whether endogenous IL-12 is required for development of EAU. IL-12 p40-deficient mice (12KO) were resistant to EAU induced with the uveitogenic retinal Ag interphotoreceptor retinoid binding protein (IRBP). Delayed hypersensitivity to IRBP was marginally reduced, whereas Ag-specific proliferation was enhanced. Primed lymphocytes of wild-type (wt) mice, cultured with IRBP, produced a Th1-like cytokine profile and transferred EAU to syngeneic wt recipients. Interestingly, the same cells were inefficient in transferring EAU to 12KO recipients, unless IL-12 was included in the culture. Primed cells of the 12KO mice produced a Th2-like cytokine profile and failed to transfer EAU. However, when IL-12 was added to the culture, 12KO cells produced large amounts of IFN-γ and transferred EAU to naive 12KO recipients. We conclude that resistance to EAU of 12KO mice is not due to an inherent inability of these mice to develop ocular disease. Despite an apparent similarity in Ag-specific cytokine responses to IFN-γ-deficient mice, 12KO mice have inhibited generation of uveitogenic effector cells, a situation that can be reversed even after priming, by adding exogenous IL-12 ex vivo. Lastly, the diminished ability of primed wt lymphocytes to induce EAU in 12KO mice indicates a role for endogenous IL-12 in the efferent phase of disease expression that is distinct from its role during Ag priming.

Factors Involved in the Differentiation of TGF-β-Producing Cells from Naive CD4+ T Cells: IL-4 and IFN-γ Have Opposing Effects, While TGF-β Positively Regulates Its Own Production

TGF-β has been shown to play a central role in regulating inflammatory responses; thus, understanding the factors involved in the generation of TGF-β-producing cells could lead to interventions that are useful in effecting disease progression. In initial studies, the capacity of naive CD4+ T cells from TCR transgenic (Tg) mice to produce TGF-β following primary and secondary stimulation was assessed. TGF-β, IL-4, or IFN-γ production could not be detected from highly purified naive CD4+/lymphocyte endothelial cell adhesion molecule (LECAM)-1high cells following primary stimulation for 36 h with plate-bound anti-CD3, anti-CD28, and IL-2. This population was subsequently used to study the differentiation of TGF-β-producing CD4+ T cells. In further studies, naive CD4+/LECAM-1high cells from TCR transgenic mice of both the BALB/c and B10.A backgrounds were stimulated with T-depleted spleen cells (TDS) and specific peptide in the presence of various cytokines and/or cytokine antagonists for 5 days, restimulated, and TGF-β, IL-4, and IFN-γ production were measured. Priming conditions favoring high IL-4 production and/or low IFN-γ production greatly enhanced TGF-β production in secondary cultures. Furthermore, the presence of IL-10 in cultures was associated with an increase in TGF-β production following restimulation. The importance of IL-4 and IFN-γ in regulating TGF-β production was confirmed in studies showing that cells from IFN-γ−/− mice produced more TGF-β, while cells from IL-4−/− mice produced less TGF-β compared with wild-type controls. Finally, the addition of exogenous TGF-β to priming cultures significantly enhanced the production of TGF-β upon restimulation, demonstrating that TGF-β has a role in self-regulating its own production.