IL-33: a Janus cytokine.

Interleukin (IL) 33, a member of the IL-1 family, is the ligand of ST2 that is expressed mainly on activated Th2 cells and mast cells. IL-33 can skew a predominantly Th1 cell population to a mainly Th2 cells phenotype in vivo. IL-33 messenger RNA is expressed early during infection of the intestinal-dwelling nematode Trichuris muris in mice. IL-33 treatment enhances resistance to Trichuris infection. IL-33 also effectively attenuates sepsis by mobilising the innate cells, neutrophils, to the site of infection, helping to clear the pathogens. Thus, IL-33 may be evolutionally preserved for the host defence against infections. IL-33 can reduce an ongoing atherosclerosis in ApoE(-/-) mice and attenuate adipocytes mainly by inducing the production of type II cytokines. In contrast, IL-33 can also exacerbate allergy and the inflammation in collagen-induced or serum-induced arthritis. Hence, IL-33 is a double-edged sword, and targeting IL-33 should be approached with caution.

Interleukin-33 amplifies IgE synthesis and triggers mast cell degranulation via interleukin-4 in naïve mice.

BACKGROUND: The regulation and function of IgE in healthy individuals and in antigen-naïve animals is not well understood. IL-33 administration increases serum IgE in mice with unknown mechanism. We tested the hypothesis that IL-33 provides an antigen-independent stimulus for IgE production and mast cell degranulation. METHODS: IL-33 was administered to naïve wild-type (WT), nude and ST2(-/-) , IL-4(-/-) , IL4Rα(-/-) and T-or B-cell-specific IL-4Rα(-/-) mice. IgE and cytokines were quantified by ELISA. T- and B-lymphocyte numbers and CD40L expression were determined by flow cytometry. Anaphylaxis was measured by temperature, mast cell degranulation and histamine release. RESULTS: IL-33 enhanced IgE production in naïve WT, T-IL-4Rα(-/-) but not in ST2(-/-) , IL-4(-/-) , IL-4Rα(-/-) or B-cell-specific IL-4Rα(-/-) mice, demonstrating IL-33 specificity and IL-4 dependency. Moreover, IL-4 was required for IL-33-induced B-cell proliferation and T-cell CD40L expression, which promotes IgE production. IL-33-induced IL-4 production was mainly from innate cells including mast cells and eosinophils. IL-33 increased mast cell surface IgE and triggered degranulation and systemic anaphylaxis in allergen-naïve WT but not in IL-4Rα(-/-) mice. CONCLUSION: IL-33 amplifies IgE synthesis and triggers anaphylaxis in naïve mice via IL-4, independent of allergen. IL-33 may play an important role in nonatopic allergy and idiopathic anaphylaxis.

Interleukin-15 mediates T cell-dependent regulation of tumor necrosis factor-alpha production in rheumatoid arthritis.

Tumor necrosis factor-alpha occupies a central role in rheumatoid arthritis (RA) pathogenesis. We now report that interleukin-15 (IL-15) can induce TNF-alpha production in RA through activation of synovial T cells. Peripheral blood (PB) T cells activated by IL-15 induced significant TNF-alpha production by macrophages via a cell-contact-dependent mechanism. Freshly isolated RA synovial T cells possessed similar capability, and in vitro, IL-15 was necessary to maintain this activity. IL-15 also induced direct TNF-alpha production by synovial T cells. In contrast, IL-2 induced significantly lower TNF-alpha production in either cell-contact-dependent or direct culture, and IL-8 and MIP-1 alpha were ineffective. Antibodies against CD69, LFA-1 or ICAM-1 significantly inhibited the ability of T cells to activate macrophages by cell contact.

The role of interleukin-15 in T-cell migration and activation in rheumatoid arthritis.

Interleukin 15 (IL-15) is a novel cytokine with interleukin-2-like activity. It is also a potent T-lymphocyte chemoattractant. Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by the presence of activated T lymphocytes, macrophages and synoviocytes in the synovial membrane. The mechanisms of T-cell activation in RA are currently unclear. We report the presence of high concentrations of IL-15 in rheumatoid arthritis (RA) synovial fluid and have demonstrated its expression in the synovial membrane lining layer by immunohistochemistry. RA synovial fluids were found to contain chemotactic activity, which was attributable in part to the presence of IL-15. Moreover, in a murine model, injection of recombinant IL-15 was found to induce a local tissue inflammatory infiltrate consisting predominantly of T lymphocytes. Synovial fluid T lymphocytes proliferate in response to IL-15, demonstrating that continued responsiveness to IL-15 is a feature of T cells after entry into the synovial compartment. These data suggest that IL-15 can recruit and activate T lymphocytes in the synovial membrane, thereby contributing to RA pathogenesis.

Chemoattraction of human blood T lymphocytes by interleukin-15.

Recombinant interleukin (IL)-15, derived from a simian kidney epithelial cell line, is a chemoattractant for human blood T lymphocytes judged by its ability to increase the proportion of cells in polarized morphology, to stimulate invasion of collagen gels containing IL-15, and to increase the proportion of locomotor cells observed by time-lapse videorecording. The ability of lymphocytes to respond was partly, but not completely, inhibited by pretreatment with anti-IL-2 receptor beta-chain. The activity of IL-15 was completely abolished by preincubation with aIL-15 but unaffected by preincubation with aIL-2. No response of monocytes, neutrophils, or B lymphocytes to IL-15 was observed.

Immunological regulation of experimental cutaneous leishmaniasis. III. Nature and significance of specific suppression of cell-mediated immunity in mice highly susceptible to Leishmania tropica.

BALB/c mice have been an exceptional susceptibility to Leishmania tropica infection such that cutaneous lesions grow without restraint in all cases leading to fatal metastasis and visceralization in normal and x-irradiated, bone-marrow reconstituted (XBM) animals. Adult thymectomized, x-irradiated, bone marrow-reconstituted (ATxXBM) BALB/c mice, however, show pronounced retardation of lesion growth leading to some survival and even cures. A similar trend was also found in moderately susceptible (BALB/c X C57BL/6)F1 mice, in contrast with the "resistant" CBA strain, in which, as previously known, ATxXBM animals showed impairment of normal, spontaneous self-healing. These convere effects are paralleled by respective leishmania-specific delayed-type hypersensitivity (DTH) reactivities, prior thymectomy leading to diminution in CBA and augmentation in BALB/c and (BALB/c X C57BL/6)F1. Anti-leishmanial DTH responses, amplfiable by cyclophosphamide pretreatment, can be detected in BALB/c mice within 10 d of infection with 2 X 10(7) promastigotes, but becomes near-totally suppressed by day 25-35. No such suppressin is found in CBA, C57BL/6, or (BALB/c X C57BL/6)F1 mice together with varying degrees of immune control of lesion development or regression. Suppression of DTH in BALB/c mice is leishmania specific and does not extent to 2,4-dinitrofluorobenzene (DNFB) or sheep erythrocytes specificities. Spleen cells from suppressed L. tropica-infected mice when transferred to normal BALB/c mice impaired the induction of DTH to leishmanial antigen. This property resided in the T cell-enriched fraction and not in the T cell-depleted fraction. It is concluded that a major component of the striking inability of BALB/c mice to control L. tropica infection involves profound impairment of a potentially curative cell-mediated immune response by suppressor T cell generation. The possibility is discussed that this may be secondary to rapid amastigote (antigen) accumulation in macrophages expressing the primary genetic "defect."

Delayed-type hypersensitivity to influenza virus. Induction of antigen-specific suppressor T cells for delayed-type hypersensitivity to hemagglutinin during influenza virus infection in mice.

Mice infected with A/England/939/69 X A/Puerto Rico/8/34 (Rec 31) influenza virus by aerosol develop significantly lower levels of delayed-type hypersensitivity (DTH) to A/Hong Kong/1/68 X A/Puerto Rico/8/34/ (X31) virus compared to uninfected mice. The suppression of DTH to the hemagglutinin appears to be mediated by suppressor T cells which carry Lyt-1 membrane antigen marker, and not by sy serum antibody. The suppressor T cells for DTH induced by Rec 31 virus (H3N1) infection suppress the DTH response to the variants of the H3 subtype of influenza viruses, but have no effect on the DTH responses to A/Puerto Rico/8/34 virus (H0N1), a B influenza virus or the matrix protein of type A influenza virus. Suppressor T cells for DTH appear 2 wk after infection and are detectable in the spleen for at least 40 d thereafter. T-helper cells for antibody response to hemagglutinin are induced concomitantly with the T-suppressor cells for DTH. Possible implications of the present findings on the regulation of the immune response to viral infection are discussed.

Immunity in taeniasis-cysticercosis I. Vaccination against Taenia taeniaeformis in rats using purified antigen.

Artificial immunization of rats against Taenia taeniaeformis was studied using somatic antigen (Som-Ag) and excretory-secretory antigen (ES-Ag). It was found that both Som-Ag and ES-Ag stimulated immediate-type hypersensitivity and delayed-type hypersensitivity reactions of similar levels. Antibody levels rose from the 2nd wk and peaked around the 6th and 7th wk. Both IgM and IgG were detectable from the 2nd wk onwards, with IgG at a considerably higher level compared to IgM. It terms of protection, 90-100% reduction in cyst counts were detected if the rats were challenged 10 days or more after immunization. In all cases, no significant difference was observed between immunization with either Som-Ag or ES-Ag were purified and characterized using Sephadex G-200 chromatography, double immunodiffusion, and disk acrylamide gel electrophoresis. A purified antigen (mol wt, 140,000 daltons) was obtained, and highly significant protection against infection resulted with injections of 50, 10, or 1 mug doses of this antigen with complete Freund's adjuvant.

Lack of a correlation between cell-mediated immunity to the carrier and the carrier-hapten helper effect.

The relationship between cell-mediated immunity to the carrier and the carrier-hapten helper effect was studied in the rat by using three forms of the carrier which differed in their capacity to induce carrier-specific delayed-type hypersensitivity. The three carriers were polymerized flagellin (POL), flagellin (FIN), and acetoacetylated flagellin (AFIN), which induced FIN-specific delayed-type hypersensitivity in the order AFIN > FIN > POL. Helper cells for the anti-DNP antibody responses to a range of DNP-FIN conjugates appeared to be almost inversely related to cell-mediated immunity to the carrier, being in the order POL > FIN =/> AFIN. These differences occurred whether the carriers were injected in saline or FCA, but were less pronounced with the heavily DNP-conjugated flagellins.

Immunological regulation of experimental cutaneous leishmaniasis. IV. Prophylactic effect of sublethal irradiation as a result of abrogation of suppressor T cell generation in mice genetically susceptible to Leishmania tropica.

The overwhelming susceptibility of BALB/c mice to infection with Leishmania tropica can be substantially reversed by immediately prior sub-lethal irradiation. This is related to radiation dosage, and at 550 rad, causes 60 percent complete cures and only 19 percent (instead of 100 percent) incidence of progressive disease. Irradiation 10 d before infection is only weakly prophylactic, whereas 10 d after is without effect. Control of lesion development is only apparent after the first 30 d, coincident with the analogous onset previously found in resistant strains and adult thymectomized, x-irradiated, bone marrow-reconstituted BALB/c mice. Instead of the specific suppression of DTH characteristic of L. tropica infection in the BALB/c strain, healed irradiated mice express strong anti-leishmanial DTH reactivity and resistance to reinfection. T cells from these mice transfer DTH reactivity which is suppressed by admixture with cells from nonhealed, nonreactive donors. Irradiated BALB/c mice again develop inexorable disease progression, after its transient arrest, when they are reconstituted with normal T cells. When the T cells are derived from uncontrollably-infected donors, the susceptibility regained is indistinguishable from that of normal mice. B cells do not modify the prophylactic effect of 550 rad, whereas T cells from healed mice confer strong protective immunity throughout the initial phase. Regression or progression of disease correlates completely with DTH reactivity in all these groups. Although BALB/c mice express an extreme level of genetic susceptibility to L. tropica infection, they are nevertheless capable of mounting a curative cell mediated immune response. That this is ineffective during pathogenesis of the disease was previously associated correlatively with potent specific suppressor T cell generation, which is now shown to be preventable by prior irradiation. Most important, however, a causal role for these cells in vivo has been demonstrated directly by reconstitution.

Immune response to chemically modified flagellin. 3. Enhanced cell-mediated immunity during high and low zone antibody tolerance to flagellin.

High and low zone antibody tolerance to bacterial flagellin can be induced in adult strain W Wistar rats by multiple injections of a cyanogen bromide (CNBr) digest of flagellin at two widely spaced dose levels. Intermediate doses of the CNBr digest produce enhanced antibody titers to flagellin rather than antibody tolerance. Studies reported in this paper revealed that both high and low zone antibody tolerance to flagellin were accompanied by heightened levels of delayed-type hypersensitivity. Conversely, when enhancement of the antibody response occurred, suppression of delayed hypersensitivity was observed. This inverse relationship between humoral and cell-mediated immunity was very striking in strain W Wistar rats but was not quite so clear-cut in another strain of Wistar rats (strain J). Strain J rats were resistant to the induction of antibody tolerance and gave higher immunological responses to flagellin than strain W animals. In addition, it was observed that, in contrast to adult tolerance, administration of the CNBr digest to neonatal rats induced complete tolerance at the level of both humoral and cell-mediated immunity. These findings were discussed in the light of earlier studies with flagellin and provide further evidence for a previously described hypothesis.

A repetitive peptide of Leishmania can activate T helper type 2 cells and enhance disease progression.

Leishmaniasis provides a biologically relevant model to analyze the heterogeneity of CD4+ T cells and may lead to answering the major question of the mechanism for the preferential induction of T helper type 1 (Th1) and Th2 cells. Using synthetic peptides corresponding to the tandemly repeating regions of Leishmania proteins, we have identified an epitope that can preferentially induce the disease-exacerbating Th2 cells in susceptible BALB/c mice. Lymph node cells from BALB/c mice immunized subcutaneously with the octamer (p183) of the repeating 10-mer peptide EAEEAARLQA proliferated strongly against the peptide as well as the soluble antigen extract (SolAg) of Leishmania major. The proliferative T cells are CD4+, major histocompatibility complex class II restricted, and secrete interleukin 4 (IL-4) but little or no IL-2 and interferon gamma when stimulated with the peptide in vitro. T cells from BALB/c mice with progressive disease, but not from BALB/c mice cured of the infection, recognized this epitope. BALB/c mice injected subcutaneously with p183 developed significantly exacerbated disease when subsequently challenged with L. major. Furthermore, subcutaneous injection with p183 prevented the subsequent induction of resistance against L. major by intravenous immunization with soluble antigen. The T cell response to p183 is H-2d restricted. Immunization of the genetically resistant B10.D2 mice with p183 also produced strong T cell responses and exacerbated disease when challenged with L. major.

Helper T cells induced by an immunopurified herpes simplex virus type I (HSV-I) 115 kilodalton glycoprotein (gB) protect mice against HSV-I infection.

Three herpes simplex virus type I (HSV-I) glycoproteins of apparent molecular masses 103, 63, and 115 kD have been purified using virus-specific monoclonal antibodies (mAb) G8D1, C2D2, and T157, respectively. Both G8D1 and C2D2 neutralize HSV-I in vitro and passively protect CBA mice against HSV-I infection in vivo, whereas T157 is neither neutralizing nor passively protective. However, mice given a single subcutaneous injection of 30 micrograms 115 kD glycoprotein in saline were completely protected against lethal challenges of HSV-I administered intraperitoneally or in the footpad 7 d after immunization. In contrast, mice similarly immunized with 103 or 63 kD glycoproteins were only partially protected. The prophylactic immunity was correlated with an early induction of specific antibody, which became even more evident 3 d after virus challenge. There was a remarkable similarity in antibody isotype distribution between the responses to 115 kD glycoprotein and to heat-inactivated intact HSV-I. However, the prechallenge sera from 115 kD glycoprotein hyperimmunized mice were again neither virus-neutralizing nor passively protective. All three glycoproteins induced only low levels of delayed-type hypersensitivity (DTH). Pretreatment of mice with cyclophosphamide significantly enhanced DTH to 115 kD and 103 kD glycoproteins in the absence of antibody, but failed to confer significant immunity, indicating that DTH alone is insufficient for protection. Splenic and lymph node Ig- (B cell-depleted) cells from mice protectively immunized with 115 kD glycoprotein could adoptively transfer effective protection and enhance a virus neutralizing antibody response in normal recipients challenged with a lethal dose of HSV-I. Both the protection and the ability to enhance neutralizing antibody were diminished when the cells were treated with mAb GK 1.5 and complement. These results therefore demonstrate that the 115 kD glycoprotein, though not apparently containing accessible epitopes for the induction of virus-neutralizing antibody, possesses determinants capable of activating helper T cells. These L3T4+ cells confer strong protective immunity by enhancing protective antibody upon challenge infection, probably through associative help.

The role of interleukin 12 and nitric oxide in the development of spontaneous autoimmune disease in MRL/MP-lpr/lpr mice.

MRL/MP-lpr/lpr (MRL/lpr) mice develop a spontaneous autoimmune disease. Serum from these mice contained significantly higher concentrations of nitrite/nitrate than serum from age-matched control MRL/MP-+/+ (MRL/+), BALB/c or CBA/6J mice. Spleen and peritoneal cells from MRL/lpr mice also produced significantly more nitric oxide (NO) than those from the control mice when cultured with interferon (IFN) gamma and lipopolysaccharide (LPS) in vitro. It is interesting to note that peritoneal cells from MRL/lpr mice also produced markedly higher concentrations of interleukin (IL) 12 than those from MRL/+ or BALB/c mice when cultured with same stimuli. It is striking that cells from MRL/lpr mice produced high concentrations of NO when cultured cells from MRL/+ or BALB/c mice. The enhanced NO synthesis induced by IFN-gamma/LPS was substantially inhibited by anti-IL-12 antibody. In addition, IL-12-induced NO production can also be markedly inhibited by anti-IFN-gamma antibody, but only weakly inhibited by anti-tumor necrosis factor alpha antibody. The effect of IL-12 on NO production was dependent on the presence of natural killer and possibly T cells. Serum from MRL/lpr mice contained significantly higher concentrations of IL-12 compared with those of MRL/+ or BALB/c control mice. Daily injection of recombinant IL-12 led to increased serum levels of IFN-gamma and NO metabolites, and accelerated glomerulonephritis in the young MRL/lpr mice (but not in the MRL/+ mice) compared with controls injected with phosphate-buffered saline alone. These data, together with previous finding that NO synthase inhibitors can ameliorate autoimmune disease in MRL/lpr mice, suggest that high capacity of such mice to produce IL-12 and their greater responsiveness to IL-12, leading to the production of high concentrations of NO, are important factors in this spontaneous model of autoimmune disease.

Protection in simian immunodeficiency virus-vaccinated monkeys correlates with anti-HLA class I antibody response.

Our earlier reports demonstrated that Cynomolgus macaques vaccinated with either inactivated partially purified simian immunodeficiency virus (SIV), fixed SIV-infected C8166 (a human T lymphoblastoid cell line) cells, or fixed uninfected C8166 cells can be protected against a challenge infection with the 32H isolate of SIVmac 251 (grown in C8166) (Stott, E. J., W. L. Chan, K. H. G. Mills, M. Page, F. Taffs, M. Cranage, P. Greenway, and P. Kitchin. 1990. Lancet. 336:1538; Stott, E. J., P. A. Kitchin, M. Page, B. Flanagan, L. F. Taffs, W. L. Chan, K. H. G. Mills, P. Silvera, and A. Rodgers. 1991. Nature [Lond.]. 353:393). Protection is correlated with the levels of antibody response to cellular antigens in the human cells from which the virus immunogen was grown. However, the mechanism of protection is unclear. We report here the analysis of sera from these protected monkeys and demonstrate that there is positive correlation of protection with antibody response to the HLA class I molecule.

Selective expression of a stable cell surface molecule on type 2 but not type 1 helper T cells.

T helper cell type 1 (Th1) and 2 (Th2) are central to immune regulation. However, no stable cell surface marker capable of distinguishing and separating these two subsets of CD4(+) cells has yet been found. Using differential display PCR, we have identified a gene encoding a cell membrane bound molecule, originally designated ST2L, T1, DER4, or Fit, expressed constitutively and stably on the surface of murine Th2s, but not Th1s even after stimulation with a range of immunological stimuli. Antibody against a peptide derived from ST2L strongly and stably labeled the surface of cloned Th2s but not Th1s, and Th2s but not Th1s derived from naive T cells of ovalbumin T cell receptor-alpha/beta transgenic mice. Three-color single cell flow cytometric analysis shows that cell surface ST2L coexpressed with intracellular interleukin (IL)-4, but not with interferon (IFN)-gamma. The antibody selectively lysed Th2s in vitro in a complement-dependent manner. In vivo, it enhanced Th1 responses by increasing IFN-gamma production and decreasing IL-4 and IL-5 synthesis. It induced resistance to Leishmania major infection in BALB/c mice and exacerbated collagen-induced arthritis in DBA/1 mice. Thus, ST2L is a stable marker distinguishing Th2s from Th1s and is also associated with Th2 functions. Hence, it may be a target for therapeutic intervention.

Production of nitric oxide in the synovial membrane of rheumatoid and osteoarthritis patients.

We have demonstrated spontaneous nitric oxide (NO) production by primary synovial cultures from rheumatoid (RA) and osteoarthritis patients. Increased NO production followed addition of staphylococcal enterotoxin B. Immunochemical double staining with specific anti-human inducible NO synthase (iNOS) and nonspecific esterase (NSE), or anti-CD68 (markers for tissue macrophages) showed that although many lining layer cells in RA synovium expressed iNOS, most (approximately 90%) were NSE- and CD68-, with only a minor population (approximately 10%) which were iNOS+, CD68+/NSE+. These data demonstrate the capacity for high output of NO by human synovial tissue and show that, although human macrophages can express high levels of iNOS, the majority of cells expressing iNOS are fibroblasts. We also report that synoviocytes, and macrophage cell lines, cultured with the NO donor, S-nitroso-acetyl penicillamine, produced high concentrations of tumor necrosis factor (TNF)-alpha. These results suggest that NO may mediate pathology in RA through the induction of TNF-alpha production.

Selective expression and functions of interleukin 18 receptor on T helper (Th) type 1 but not Th2 cells.

Interleukin (IL)-18 induces interferon (IFN)-gamma synthesis and synergizes with IL-12 in T helper type 1 (Th1) but not Th2 cell development. We report here that IL-18 receptor (IL-18R) is selectively expressed on murine Th1 but not Th2 cells. IL-18R mRNA was expressed constitutively and consistently in long-term cultured clones, as well as on newly polarized Th1 but not Th2 cells. IL-18 sustained the expression of IL-12Rbeta2 mRNA, indicating that IL-18R transmits signals that maintain Th1 development through the IL-12R complex. In turn, IL-12 upregulated IL-18R mRNA. Antibody against an IL-18R-derived peptide bound Th1 but not Th2 clones. It also labeled polarized Th1 but not Th2 cells derived from naive ovalbumin-T cell antigen receptor-alphabeta transgenic mice (D011.10). Anti-IL-18R antibody inhibited IL-18- induced IFN-gamma production by Th1 clones in vitro. In vivo, anti-IL-18R antibody reduced local inflammation and lipopolysaccharide-induced mortality in mice. This was accompanied by shifting the balance from Th1 to Th2 responses, manifest as decreased IFN-gamma and proinflammatory cytokine production and increased IL-4 and IL-5 synthesis. Therefore, these data provide a direct mechanism for the selective effect of IL-18 on Th1 but not Th2 cells. They also show that the synergistic effect of IL-12 and IL-18 on Th1 development may be due to the reciprocal upregulation of their receptors. Furthermore, IL-18R is a cell surface marker distinguishing Th1 from Th2 cells and may be a therapeutic target.

Role of interleukin 33 in human immunopathology.

Interleukin 33 (IL33) is a recently described member of the IL1 superfamily of cytokines. Originally defined on the basis of T-cell subset differentiation, IL33 is now recognised to mediate a wider role in regulating components of the innate immune response also, particularly via mast cell activation. In this paper the basic biology of IL33 is described together with that of its cognate receptor, ST2L, and the existing knowledge base for its potential role in mediating human pathology across a range of diseases is defined.

The role of TH1 and TH2 cells in a rodent malaria infection.

CD4+ T cells play a major role in protective immunity against the blood stage of malaria, but the mechanism of protection is unclear. By adoptive transfer of cloned T cell lines, direct evidence is provided that both TH1 and TH2 subsets of CD4+ T cells can protect mice against Plasmodium chabaudi chabaudi infection. TH1 cells protect by a nitric oxide-dependent mechanism, whereas TH2 cells protect by the enhancement and accelerated production of specific immunoglobulin G1 antibody.