TMC-256A1 and C1, new inhibitors of IL-4 signal transduction produced by Aspergillus niger var niger TC 1629

New inhibitors of IL-4 signal transduction, designated as TMC-256A1 and C1, were discovered together with TMC-256B1, a previously known dihydronaphthopyrone, from the fermentation broth of Aspergillus niger var niger TC 1629 by using an IL-4 driven reporter gene assay. Based on spectroscopic analyses, TMC-256A1 and C1 were found to be new members of the naphthopyrone antibiotics. TMC-256A1, B1 and C1 inhibited the IL-4 driven luciferase activity with IC50 values of 25 microM, 30 microM and 1.7 microM, respectively in this assay system. Furthermore, these compounds inhibited the expression of germline C epsilon mRNA with IC50 values of 6.6 microM , 34 microM and 0.31 microM, respectively.

HIV-1 matrix protein p17 increases the production of proinflammatory cytokines and counteracts IL-4 activity by binding to a cellular receptor

Purified recombinant HIV-1 p17 matrix protein significantly increased HIV-1 replication in preactivated peripheral blood mononuclear cell cultures obtained from healthy donors. Because HIV-1 infection and replication is related to cell activation and differentiation status, in the present study, we investigated the role played by p17 during the process of T cell stimulation. Using freshly isolated peripheral blood mononuclear cells, we demonstrate that p17 was able to enhance levels of tumor necrosis factor alpha and IFN-gamma released from cells stimulated by IL-2. IL-4 was found to down-regulate IFN-gamma and tumor necrosis factor alpha, and p17 restored the ability of cells to produce both cytokines. The property of p17 to increase production of proinflammatory cytokines could be a mechanism exploited by the virus to create a more suitable environment for HIV-1 infection and replication. Our data show that p17 exerts its biological activity after binding to a specific cellular receptor expressed on activated T lymphocytes. The functional p17 epitope involved in receptor binding was found to be located at the NH(2)-terminal region of viral protein. Immunization of BALB/c mice with a 14-aa synthetic peptide representative of the HIV-1 p17 functional region (SGGELDRWEKIRLR) resulted in the development of p17 neutralizing antibodies capable of blocking the interaction between p17 and its cellular receptor. Our results define a role for p17 in HIV-1 pathogenesis and contribute to our understanding of the molecular mechanism of HIV-1 infection and the development of additional antiviral therapeutic strategies.

[Eosinophil inflammation of the nasal mucosa]

INTRODUCTION

Inflammatory diseases are very frequent and cause reasonable mortality. They are the major part in upper airway diseases in ENT. Eosinophil inflammation is a key feature in allergic rhinitis, asthma, nasal polyps and non-allergic rhinitis. The mechanism and the consequences of eosinophil inflammation are described in this review.

METHODS AND RESULTS

Eosinophils mature in bone marrow, mainly under the influence of IL-5 and eotaxin. Once mobilised to circulation, they accumulate in inflammatory sites by specific adhesion. VCAM-1 and other adhesion molecules are involved in this process. In the tissue, eosinophils get activated by different stimuli like immunoglobulin receptors and cytokines like IL-5. Activated eosinophils release toxic proteins, mediators and cytokines and thus trigger further inflammatory response. This leads to the late phase reaction and continuing inflammatory reaction. Eosinophils also interact with virus infections and have effects on nerve endings with the M2 receptor.

CONCLUSIONS

Eosinophil inflammation may be monitored via the determination of cationic proteins in nasal secretions. Corticosteroids are very effective in the treatment of eosinophil inflammation, and anti-IL-5 and anti-IL-4 antibodies seem to be effective, too.

Role of IFN-gamma in Th1 differentiation: IFN-gamma regulates IL-18R alpha expression by preventing the negative effects of IL-4 and by inducing/maintaining IL-12 receptor beta 2 expression

Two key events occur during the differentiation of IFN-gamma-secreting Th1 cells: up-regulation of IL-12Rbeta2 and IL-12-driven up-regulation of IL-18Ralpha. We previously demonstrated that IL-12-driven up-regulation of IL-18Ralpha expression is severely impaired in IFN-gamma(-/-) mice. However, it was unclear from these studies how IFN-gamma influenced IL-18Ralpha since IFN-gamma alone had no direct effect on IL-18Ralpha expression. In the absence of IL-4, IL-12-dependent up-regulation of IL-18Ralpha/IL-12Rbeta2 was independent of IFN-gamma. However, in the presence of IL-4, IFN-gamma functions to limit the negative effects of IL-4 on both IL-18Ralpha and IL-12Rbeta2. Neutralization of IL-4 restored IL-12-driven up-regulation of IL-18Ralpha/IL-12Rbeta2 in an IFN-gamma-independent fashion. In the absence of both IL-12 and IL-4, IFN-gamma up-regulates IL-12beta2 expression and primes IFN-gamma-producing Th1 cells. When T cells were primed in the presence of IL-4, no correlation was found between the levels of expression of the IL-18Ralpha or the IL-12Rbeta2 and the capacity of these cells to produce IFN-gamma, suggesting that IL-4 may also negatively affect IL-12-mediated signal transduction and thus Th1 differentiation. These data clarify the role of IFN-gamma in regulation of IL-18Ralpha/IL-12Rbeta2 during both IL-12-dependent and IL-12-independent Th1 differentiation.

Sustained NFAT signaling promotes a Th1-like pattern of gene expression in primary murine CD4+ T cells

T cell activation is known to be critically regulated by the extent and duration of TCR-induced signaling pathways. The NFAT family of transcription factors is believed to play an important role in coupling these quantitative differences in TCR-induced signaling events into changes in gene expression. In this study we have specifically investigated the effects of sustained NFAT signaling on T cell activation by introducing a constitutively active mutant version of NFATc1 (caNFATc1) into primary murine CD4(+) T cells and examining its effects on gene expression. We now report that ectopic expression of caNFATc1 partially mimics TCR signaling, resulting in enhanced expression of CD25 and CD40 ligand and down-regulation of CD62L. More importantly, we find that expression of caNFATc1 in T cells maintained under either nonpolarizing or Th1-skewing conditions leads to a marked selective increase in the number of cells expressing the prototypical Th1 cytokine, IFN-gamma. Furthermore, when expressed in Th2-skewed cells, caNFATc1 appears to attenuate Th2 differentiation by decreasing production of IL-4 and promoting the expression of IFN-gamma. Finally, we find that caNFATc1 enhances expression of functional P-selectin glycoprotein ligand-1, up-regulates Fas ligand expression, and increases susceptibility to activation-induced cell death, cellular traits that are preferentially associated with Th1 effector cells. Taken together, these results suggest that sustained NFAT signaling, mediated by ectopic expression of caNFATc1, acts to promote a Th1-like pattern of gene expression and thereby serves to highlight the important relationship between the degree of NFAT signaling and the qualitative pattern of gene expression induced during T cell activation.

Death ligand TRAIL induces no apoptosis but inhibits activation of human (auto)antigen-specific T cells

TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily, induces apoptosis in susceptible cells, which can be both malignant and nontransformed. Despite homologies among the death ligands, there are great differences between the TRAIL system on the one hand and the TNF and CD95 systems on the other hand. In particular, TRAIL-induced apoptosis differs between rodents and man. Studies on animal models of autoimmune diseases suggested an influence of TRAIL on T cell growth and effector functions. Because we previously demonstrated that TRAIL does not induce apoptosis in human (auto)antigen-specific T cells, we now asked whether TRAIL exhibits other immunoregulatory properties in these cells. Active TRAIL inhibited calcium influx through store-operated calcium release-activated calcium channels, IFN-gamma/IL-4 production, and proliferation. These effects were independent of APC, Ag specificity, and Th differentiation, and no differences were detected between healthy donors and multiple sclerosis patients. TRAIL affected neither the expression of the cell cycling inhibitor p27(Kip1) nor the capacity of T cells to produce IL-2 upon Ag rechallenge, indicating that signaling via TRAIL receptor does not induce T cell anergy. Instead, the TRAIL-induced hypoproliferation could be attributed to the down-regulation of the cyclin-dependent kinase 4, indicating a G(1) arrest of the cell cycle. Thus, although it does not contribute to mechanisms of peripheral T cell tolerance such as clonal anergy or deletion by apoptosis, TRAIL can directly inhibit activation of human T cells via blockade of calcium influx.

Corticosteroid inhibits IL-4 signaling through down-regulation of IL-4 receptor and STAT6 activity

Corticosteroids are potent anti-inflammatory and immunosuppressive agents which down-regulate cytokine production and action. Yet, contradictory results have been reported for their effects on the interleukin (IL)-4-mediated response. Using type II Fc receptor for IgE/CD23 as a target gene, here we report that corticosteroids at 10(-4)-10(-6) M inhibit the IL-4 signaling pathway in human primary immune cells by down-regulation of the IL-4-induced IL-4 receptor expression and STAT6 activation. Although functional antagonism between steroid receptor and STAT6 for their transcriptional activity has been recently described, this is the first report that steroid inhibits the IL-4-induced STAT6 activity at the level of tyrosine phosphorylation and target DNA binding.

[Asthma: prevalence, pathogenesis and perspectives on new treatments]

Asthma is a complex clinical syndrome with many phenotypes in both children and adults. Its major characteristics include airway inflammation and obstruction, bronchial hyper-responsiveness. The disease has its roots in infancy, and both genetic and environmental factors contribute to its inception and clinical evolution. The prevalence of asthma in increasing around the world. Hypotheses that attempt to explain the rising prevalence have been advanced but remain unproven. To understand its pathogenesis it is essential to identify factors that modulate or intensify the inflammatory response of the airways. The association of allergic asthma with immune responses mediated by TH-2 cells and IgE antibodies has came to the forefront of medical research. Significant advances in understanding the immunology of asthma are being translated into specific therapies, some of which hold promise for disease modification.

Photochemical preparation of a pyridone containing tetracycle: a Jak protein kinase inhibitor

Jak3 is a protein tyrosine kinase that is associated with the shared gamma chain of receptors for cytokines IL2, IL4, IL7, IL9, and IL13. We have discovered that a pyridone-containing tetracycle (6) may be prepared from trisubstituted imidazole (5) in high yield by irradiation with >350 nm light. Compound 6 inhibits Jak3 with K(I)=5 nM; it also inhibits Jak family members Tyk2 and Jak2 with IC(50)=1 nM and murine Jak1with IC(50)=15 nM. Compound 6 was tested as an inhibitor of 21 other protein kinases; it inhibited these kinases with IC(50)s ranging from 130 nM to >10 microM. Compound 6 also blocks IL2 and IL4 dependent proliferation of CTLL cells and inhibits the phosphorylation of STAT5 (an in vivo substrate of the Jak family) as measured by Western blotting.

Cytokine modulators as novel therapies for asthma

Cytokines play a critical role in orchestrating and perpetuating inflammation in asthmatic airways and several specific cytokine and chemokine inhibitors are now in development for the treatment of asthma. Inhibition of IL-4 with soluble IL-4 receptors has shown promising early results in asthma. Anti-IL-5 antibody is very effective at inhibiting peripheral blood and airway eosinophils but does not appear to be effective in symptomatic asthma. Inhibitory cytokines, such as IL-10, interferons, and IL-12 are less promising because systemic delivery produces intolerable side effects. Inhibition of TNF-alpha may be useful in severe asthma. Many chemokines are involved in the inflammatory response of asthma, and small-molecule inhibitors of chemokine receptors are in development. CCR3 antagonists are now in clinical development for the treatment of asthma. Because so many cytokines are involved in asthma, drugs that inhibit the synthesis of multiple cytokines may prove to be more useful. Several such classes of drug are now in clinical development, and the risk of side effects with these nonspecific inhibitors may be reduced by the inhaled route of delivery.

Inhibitory effects of whole and parotid saliva on immunomodulators

Based on the presence of cytokines in whole saliva and their association with resistance and susceptibility to infectious disease, the present study was designed to evaluate the diagnostic potential of a large panel of cytokines and chemokines in saliva. Despite the endogenous presence of Th1/Th2 and pro-inflammatory cytokines and several chemokines in whole and parotid saliva of most individuals tested, the detection of known concentrations of several recombinant cytokines and chemokines was inhibited immediately following their addition to each type of saliva. In contrast, purified immunoglobulins were unaffected by either whole or parotid saliva. Further studies revealed that the inhibition of immunoreactivity involved sequestration of the majority of cytokines affected and degradation of chemokines. These results suggest that absolute concentrations of cytokines/chemokines may not be fully detectable in saliva. Therefore, the diagnostic value of any cytokine/chemokine is questionable and should be evaluated independently as such.

Mitogenic synergy through multilevel convergence of hepatocyte growth factor and interleukin-4 signaling pathways

Hepatocyte growth factor (HGF) regulates various physiological and developmental processes in concert with other growth factors, cytokines and hormones. We examined interactions between cell signaling events elicited by HGF and the cytokine interleukin (IL)-4, in the IL-3-dependent murine myeloid cell line 32D transfected with the human HGF receptor, c-Met. HGF was a potent mitogen in these cells, and prevented apoptosis in response to IL-3 withdrawal. IL-4 showed modest anti-apoptotic activity, but no significant mitogenic activity. IL-4 synergistically enhanced HGF-stimulated DNA synthesis, whereas only additive prevention of apoptosis was observed. IL-4 did not enhance HGF-dependent tyrosine phosphorylation of c-Met or Shc. In contrast, HGF-stimulated activation of MAP kinases was enhanced by IL-4, suggesting that the IL-4 and HGF signaling pathways converge upstream of these events. Although phosphatidylinositol 3-kinase (PI3K) inhibitors diminished HGF-induced mitogenesis, anti-apoptosis, and MAP kinase activation, IL-4 enhanced HGF signaling persisted even in the presence of these inhibitors. IL-4 enhancement of HGF signaling was partially blocked in 32D/c-Met cells treated with inhibitors of MEK1 or c-Src kinases, completely blocked by expression of a catalytically inactive mutant of Janus kinase 3 (Jak3), and increased in 32D/c-Met cells overexpressing STAT6. Our results suggest that the IL-4 and HGF pathways converge at multiple levels, and that IL-4-dependent Jak3 and STAT6 activities modulate signaling events independent of PI3K to enhance HGF-dependent mitogenesis in myeloid cells, and possibly other common cellular targets.

DC-SIGN (CD209) expression is IL-4 dependent and is negatively regulated by IFN, TGF-beta, and anti-inflammatory agents

Dendritic cell-specific ICAM-3 grabbing nonintegrin (DC-SIGN) is a monocyte-derived dendritic cell (MDDC)-specific lectin which participates in dendritic cell (DC) migration and DC-T lymphocyte interactions at the initiation of immune responses and enhances trans-infection of T cells through its HIV gp120-binding ability. The generation of a DC-SIGN-specific mAb has allowed us to determine that the acquisition of DC-SIGN expression during the monocyte-DC differentiation pathway is primarily induced by IL-4, and that GM-CSF cooperates with IL-4 to generate a high level of DC-SIGN mRNA and cell surface expression on immature MDDC. IL-4 was capable of inducing DC-SIGN expression on monocytes without affecting the expression of other MDDC differentiation markers. By contrast, IFN-alpha, IFN-gamma, and TGF-beta were identified as negative regulators of DC-SIGN expression, as they prevented the IL-4-dependent induction of DC-SIGN mRNA on monocytes, and a similar inhibitory effect was exerted by dexamethasone, an inhibitor of the monocyte-MDDC differentiation pathway. The relevance of the inhibitory action of dexamethasone, IFN, and TGF-beta on DC-SIGN expression was emphasized by their ability to inhibit the DC-SIGN-dependent HIV-1 binding to differentiating MDDC. These results demonstrate that DC-SIGN, considered as a MDDC differentiation marker, is a molecule specifically expressed on IL-4-treated monocytes, and whose expression is subjected to a tight regulation by numerous cytokines and growth factors. This feature might help in the development of strategies to modulate the DC-SIGN-dependent cell surface attachment of HIV for therapeutic purposes.

IL-13R(alpha)2, a decoy receptor for IL-13 acts as an inhibitor of IL-4-dependent signal transduction in glioblastoma cells

Interleukin (IL)-4 and IL-13 share the type II IL-4 receptor for cell signaling. We show that despite expressing the necessary signaling components, glioblastoma cells failed to respond to either IL-4 or IL-13. This was in part because of the expression of a high-affinity IL-13-binding transmembrane protein IL-13R(alpha)2 that inhibited IL-13-mediated Stat6 activation by acting as a decoy receptor. In contrast, normal human astrocytes that did not express the IL-13R(alpha)2 gene efficiently induced Stat6 activation in response to both IL-4 and IL-13. Transient expression of the IL-13R(alpha)2 transgene in nonexpressing heterologous cells inhibited not only IL-13- but also IL-4-mediated signal transduction and Stat6-responsive gene expression. The inhibition was likely mediated through the physical interaction between the short intracellular domain of the IL-13R(alpha)2 protein and the cytoplasmic domain of the IL-4R(alpha) chain that harbors the Stat6 docking sites. Thus, IL-13R(alpha)2 acts as an inhibitor of IL-4-dependent signal transduction pathways via a novel mechanism that is independent of ligand binding.

1,25-dihydroxyvitamin D3 inhibits IFN-gamma and IL-4 levels during in vitro polarization of primary murine CD4+ T cells

Following their activation, naive CD4+ T cells can differentiate into one of two effector cell subsets, Th1 and Th2. These two subsets have different cytokine secretion patterns and thus mediate separate arms of the immune response. It has been established that the fat-soluble vitamin D(3) metabolite 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and its nuclear receptor, the vitamin D receptor, play an important role in the immune system primarily through the transcriptional inhibition of cytokine genes that either are required for Th1 differentiation or are products of differentiated Th1 cells. Therefore, we wanted to test directly the ability of 1,25(OH)(2)D(3) to alter the Th differentiation process. Our results indicate that 1,25(OH)(2)D(3) inhibits not only the Th1 cytokine IFN-gamma but also the Th2 cytokine IL-4 in naive CD62 ligand+CD4+ T cells during their in vitro polarization. This effect is most dramatic when the ligand is present from the onset of the differentiation process. If the ligand is added after the polarization has ensued, the inhibition is significantly diminished. In activated (CD62 ligand-CD4+) T cells, 1,25(OH)(2)D(3) is still able to inhibit IFN-gamma but has no effect on IL-4 production. Our results also indicate that inhibition of these two cytokines in naive cells by vitamin D receptor and its ligand is neither a result of a cell cycle block nor an inhibition of Th1 or Th2 transcription factor expression but, rather, at least in the case of Th2 differentiation, an attenuation of IL-4 transcription by the receptor.

Aspirin and salicylates inhibit the IL-4- and IL-13-induced activation of STAT6

Allergic diseases, including asthma, represent a major threat to human health. Over the three last decades, their incidence has risen in western countries. Aspirin treatment has been shown to improve allergic diseases, especially asthma, and the decreased use of aspirin has been hypothesized to contribute to the increase in childhood asthma. Because salicylate compounds suppress a number of enzymatic activities, and signaling through IL-4R participates in the development of allergic responses, we tested the effect of salicylates on IL-4 signal transduction. We found that treatment of cell lines and primary cells with aspirin and salicylates, but not acetaminophen, inhibited the activation of STAT6 by IL-4 and IL-13. This effect correlated with the inhibition of IL-4-induced CD23 expression. Although salicylates inhibited the in vivo activation of Janus kinases, their kinase activity was not affected in vitro by salicylates, suggesting that other kinases were involved in IL-4-induced STAT6 activation. Furthermore, we found that an Src kinase was involved in STAT6 activation because 1) Src kinase activity was induced by IL-4, 2) Src kinase activity, but not Janus kinase, was inhibited by salicylates in vitro, 3) cells expressing viral Src had constitutive STAT6 phosphorylation, and 4) cells lacking Src showed low STAT6 phosphorylation in response to IL-4. Because STAT6 activation by IL-4 and IL-13 participates in the development of allergic diseases, our results provide a mechanism to explain the beneficial effects of aspirin and salicylate treatment of these diseases.

Anti-IL-4 antibody therapy causes regression of chronic lesions caused by medium-dose Leishmania major infection in BALB/c mice

Experimental infection of BALB/c mice with a high number of Leishmania major parasites results in a predominant Th2 response and rapidly progressing, non-healing lesions. Disease can be prevented in such mice by simple therapies, such as administering neutralizing anti-IL-4 or anti-CD4 antibody prior to or around the time of infection, but not once the infection is well established. Established infections can be resolved by combined therapies, such as intralesional administration of massive doses of IL-12 and of anti-leishmanial drugs. We explored the possibility of using simple therapies to cure mice with stable, chronic and large lesions, a state that corresponds more closely to human cutaneous leishmaniasis than does the rapidly progressing model. The anti-parasite immune responses of mice bearing such chronic lesions have a mixed Th1/Th2 phenotype. Administration of either anti-IL-4 or anti-CD4 antibody alone results in the reliable regression of such lesions even when large. Cured mice display a dominant Th1 response with increased L. major-specific IgG2a antibody, increased production of IL-12p40 and of nitric oxide by macrophages, indicating increased parasiticidal activity. Cured mice resist a normally pathogenic L. major challenge. These findings may have implications for treatment of human cutaneous leishmaniasis and other chronic infectious diseases caused by intracellular pathogens.

Il-4 therapy prevents the development of proteinuria in active Heymann nephritis by inhibition of Tc1 cells

The role of IL-4, a key Th2 cytokine, in promoting or inhibiting active Heymann nephritis (HN) was examined. HN is induced by immunization with Fx1A in CFA, and proteinuria in HN is associated with subepithelial IgG and C3 deposition and infiltration of CD8(+) T-cytotoxic 1 (Tc1) cells and macrophages into glomeruli, as well as induction of Abs to Crry. Treatment with rIL-4 from the time of Fx1A/CFA immunization stimulated an earlier IgG1 response to Fx1A, induced anti-Crry Abs, and up-regulated IL-4 mRNA in lymphoid tissue, but did not alter proteinuria. Treatment with MRCOx-81, an IL-4-blocking mAb, resulted in greater proteinuria, which suggests endogenous IL-4 regulated the autoimmune response. Delay of rIL-4 treatment until 4 wk post-Fx1A/CFA immunization and just before the onset of proteinuria prevented the development of proteinuria and reduced Tc1 cell infiltrate in glomeruli. Delayed treatment with IL-4 had no effect on titer or isotype of Abs to Fx1A or on Ig, C3, and C9 accumulation in glomeruli. Treatment with rIL-13, a cytokine that alters macrophage function such as rIL-4, but has no direct effect on T or B cell function, reduced glomerular macrophage infiltrate, but did not prevent proteinuria or CD8+ T cell infiltrate. Anti-Crry Abs were paradoxically only induced with rIL-4 therapy, not in HN controls with proteinuria. It was concluded that the rIL-4 effect was probably by inhibition of Tc1 cells, which normally mediate the glomerular injury that results in proteinuria.

A cytokine-to-chemokine axis between T lymphocytes and keratinocytes can favor Th1 cell accumulation in chronic inflammatory skin diseases

The recruitment of T cells into the skin is regulated by chemokines released by resident cells. In this study, we found that normal human keratinocytes activated with Th1-derived supernatant (sup) expressed early (6-12 h) IP-10/CXCL10, MCP-1/CCL2, IL-8/CXCL8, and I-309/CCL1 mRNAs and with slower kinetics (24-96 h), RANTES/CCL5 and MDC/CCL22 mRNAs. Upon stimulation with the Th1 sup, keratinocytes secreted high levels of RANTES, IP-10, MCP-1, and IL-8 and moderate levels of I-309 and MDC. Although much less efficiently, Th2 sup could also induce keratinocyte expression of IL-8, IP-10, RANTES, and MCP-1 but not of I-309 and MDC. TARC/CCL17 was not significantly induced by any stimuli. Sup from keratinocytes activated with Th1-derived cytokines elicited a strong migratory response of Th1 cells and a limited migration of Th2 cells, whereas sup from Th2-activated keratinocytes promoted a moderate migration of Th1 and Th2 lymphocytes. Thus, keratinocytes appear considerably more sensitive to Th1- than to Th2-derived lymphokines in terms of chemokine release and can support the preferential accumulation of Th1 lymphocytes in the skin.

[Inflammatory cytokines (IL-4, IL-5 and IL-13)]

The polarized Th2 cells play an important role in the pathogenesis of atopic asthma as well as in the induction of airway inflammation. Th2 cytokines, such as IL-4, IL-5 and IL-13, are pivotal in regulating the allergic phenotype, the IgE response or the inflammatory cell-mediated function. Selective inhibition of Th2 cytokines by pharmacologic agents, including anti-cytokine blocking antibody, cytokine mutant and soluble cytokine receptor, will contribute to asthma therapy. Strategies based on blocking key signaling cytokines are also discussed.

Factor VIII concentrate inhibits T helper type 2 cytokine production in vitro: relevance to inhibitor antibody formation

Inhibitor antibody formation in patients with haemophilia receiving factor VIII (FVIII) concentrate is a serious problem. T helper type 2 (Th2) cytokines are necessary for antibody production by B cells and have been shown to be produced predominantly by CD30(+)/CD45RO(+)/CD3(+) cells. We have previously shown that the Th2 cytokine, interleukin (IL)-6, is inhibited but IL-10 is upregulated, in the presence of plasma-derived FVIII (pdFVIII). To clarify further the overall effect of FVIII on Th2 cytokine production, the percentage of T cells expressing the CD30(+)/CD45RO(+)/CD3(+) Th2 phenotype was studied over 72 h and the production of the Th2 cytokines, IL-4 and IL-5, determined at 24 h in the presence of FVIII following whole-blood stimulation using multiparameter flow cytometry. The production of IL-4 and IL-5 by T cells was significantly inhibited in the presence of pdFVIII. The percentage of CD30(+)/CD45RO(+)/CD3(+) increased with stimulation of whole blood cultures over 72 h but was significantly inhibited by the presence of pdFVIII or TGF-beta at 72 h. The combined inhibitory effect of prednisolone (a commonly used immunosuppressive agent used to treat patients with inhibitors) with pdFVIII on T-cell CD30(+)/CD45RO(+) upregulation, was additive. There was no significant alteration in Th2 cytokine production or phenotype noted in the presence of recombinant FVIII (rFVIII) concentrate. Neutralizing antibody to TGF-beta significantly abrogated the inhibitory effects of pdFVIII on Th2 upregulation, indicating TGF-beta to be a major inhibitory component of pdFVIII on Th2 cytokine production. We now provide evidence that pdFVIII, by inhibiting Th2 cytokine production, may result in decreased antibody formation and may be more appropriate than rFVIII at reducing inhibitor formation. A clinical study needs to be undertaken to determine the significance of these in vitro findings.

The allergen-induced airway hyperresponsiveness in a human-mouse chimera model of asthma is T cell and IL-4 and IL-5 dependent

The cellular and molecular mechanisms involved in the airway hyperresponsiveness (AHR) of patients with allergic asthma remain unclear. A role for Th2 inflammatory cells was suggested based on murine asthma models. No direct evidence exists on the role of these cells in human asthma. The development of a mouse-human chimera might be useful, allowing the in vivo study of the components of the human immune system relevant to asthma. We investigated the role of allergen-reactive T lymphocytes in a human-mouse SCID model. SCID mice were reconstituted intratracheally with human PBMC from healthy, nonallergic, nonasthmatic donors and exposed to an aerosol of house dust mite allergen after i.p. injection with Dermatophagoides pteronyssinus I Ag and alum. The donor T lymphocytes had a Th1 cytokine phenotype. The reconstituted and allergen-challenged mice developed AHR to carbachol. The mouse airways and lungs were infiltrated with human T lymphocytes. No eosinophils or increases in human IgE were observed. The intrapulmonary human T lymphocytes demonstrated an increase in intracytoplasmic IL-4 and IL-5 and a decrease in IFN-gamma after exposure to allergen adjuvant. Antagonizing human IL-4/IL-13 or IL-5 resulted in a normalization of the airway responsiveness, despite a sustained intracellular Th2 cytokine production. These results provide evidence that the activated human allergen-reactive Th2 cells producing IL-4 or IL-5 are pivotal in the induction of AHR, whereas no critical role for eosinophils or IgE could be demonstrated. They also demonstrate that human allergen-specific Th1 lymphocytes can be driven to a Th2 phenotype.

The role of IL-4 in Heligmosomoides polygyrus-induced alterations in murine intestinal epithelial cell function

IL-4 and IL-13 promote gastrointestinal worm expulsion, at least in part, through effects on nonlymphoid cells, such as intestinal epithelial cells. The role of IL-4/IL-13 in the regulation of intestinal epithelial function during Heligmosomoides polygyrus (Hp) infection was investigated in BALB/c mice infected with Hp or treated with a long-lasting formulation of recombinant mouse IL-4/alphaIL-4 complexes (IL-4C) for 7 days. Separate groups of BALB/c mice were drug-cured of initial infection and later reinfected and treated with anti-IL-4R mAb, an antagonist of IL-4 and IL-13 receptor binding, or with a control mAb. Segments of jejunum were mounted in Ussing chambers, and short circuit current responses to acetylcholine, histamine, serotonin, PGE2, and glucose were determined. Although only modest changes in epithelial cell function were observed during primary Hp infection, IL-4C or a secondary Hp infection each induced more dramatic changes, including increased mucosal permeability, reduced sodium-linked glucose absorption, and increased Cl- secretory response to PGE2. Some, but not all, effects of IL-4C and Hp infection were dependent on enteric nerves. Hp-induced changes in epithelial function were attenuated or prevented by anti-IL-4R mAb. Thus, IL-4/IL-13 mediate many of the effects of Hp infection on intestinal epithelial cell function and do so both through direct effects on epithelial cells and through indirect, enteric nerve-mediated prosecretory effects. These immune system-independent effector functions of IL-4/IL-13 may be important for host protection against gastrointestinal nematodes.

Il-4 influences apoptosis of mycobacterium-reactive lymphocytes in the presence of TNF-alpha

T cell apoptosis is associated with defective cell-mediated effector functions in several infectious diseases. In tuberculosis, there is evidence that T cell apoptosis may be cytokine mediated, but the mechanisms are not clearly understood. Type 2 cytokines have recently been associated with disease extent in human tuberculosis, but they have not previously been linked to apoptosis in mycobacterium-reactive T cells. This study presents evidence that PBLs from healthy donors respond to sonicated Mycobacterium tuberculosis Ags with increased IL-4 gene activation, CD30 expression, and apoptosis. The changes were significantly greater than those observed when cells were stimulated with Ags from nonpathogenic Mycobacterium vaccae. A hypothesis linking these observations was tested. CD30 expression and TNF-alpha-mediated lymphocyte apoptosis were both down-regulated by inhibiting IL-4 in this model. TNFR-associated factor 2 (TRAF2) expression was down-regulated in CD30(+) cells, and addition of anti-TNF-alpha Ab significantly reduced apoptosis in the CD30(+) but not the CD30(-) population. These observations support the hypothesis that increased IL-4 expression in M. tuberculosis-activated lymphocytes promotes CD30 expression, which sensitizes the lymphocytes to TNF-alpha-mediated apoptosis via TRAF2 depletion. This may be one mechanism by which IL-4 is associated with immunopathological consequences in human tuberculosis.