Antagonistic Effects Of IL-4 Research Articles

Antagonistic Effects of IL-4 on IL-17A-Mediated Enhancement of Epidermal Tight Junction Function.

Atopic dermatitis (AD) is the most common chronic and relapsing inflammatory skin disease. AD is typically characterized by skewed T helper (Th) 2 inflammation, yet other inflammatory profiles (Th1, Th17, Th22) have been observed in human patients. How cytokines from these different Th subsets impact barrier function in this disease is not well understood. As such, we investigated the impact of the canonical Th17 cytokine, IL-17A, on barrier function and protein composition in primary human keratinocytes and human skin explants. These studies demonstrated that IL-17A enhanced tight junction formation and function in both systems, with a dependence on STAT3 signaling. Importantly, the Th2 cytokine, IL-4 inhibited the barrier-enhancing effect of IL-17A treatment. These observations propose that IL-17A helps to restore skin barrier function, but this action is antagonized by Th2 cytokines. This suggests that restoration of IL-17/IL-4 ratio in the skin of AD patients may improve barrier function and in so doing improve disease severity.

Antagonistic effects of IL-4 and interferon-gamma (IFN-gamma) on inducible nitric oxide synthase expression in bovine macrophages exposed to gram-positive bacteria.

Cytokine-mediated modulation of nitric oxide (NO) production by bacteria-stimulated bovine macrophages was studied. When Salmonella dublin, as a prototypic gram-negative organism, was used, NO generation was barely enhanced by recombinant bovine and ovine IFN-gamma, but was suppressed by IL-4. Salmonella dublin-induced NO generation was not influenced by a panel of nine other cytokines. The panel included IL-1, tumour necrosis factor (TNF) and IFN-alpha, which are active in a similar mouse macrophage model. The tested cytokines were either homologous or known to interact with bovine cytokine receptors. Recombinant bovine and ovine IFN-gamma were the only cytokines which strongly enhanced NO synthesis by macrophages exposed to the gram-positive organism, Listeria monocytogenes. Listeria-induced NO generation was strongly suppressed by recombinant human and bovine IL-4, but not by IL-10 and transforming-growth-factor-beta. Thus, two cytokines characterizing a Th1 and a Th2 response up- and down-regulate, respectively, bacteria-induced NO generation in bovine macrophages, whereas nine other cytokines had little activity in this regard. This modulation was reflected in changes in the steady state levels of mRNA coding for inducible nitric oxide synthase. Combinations of IFN-gamma and IL-4 suggested that the relative proportion of these cytokines determined whether bacteria-induced NO generation was up- or down-regulated. At saturating IL-4 concentrations, stimulation of bacteria-induced NO generation in macrophages by T cell supernatants was solely dependent on IFN-gamma. This was shown by antibody neutralization experiments and by a close correlation between the capacity of supernatants to stimulate NO generation and the IFN-gamma content, as determined by immunoassay.

Pivotal Role of Interleukin-12 and Interferon-γ Axis in Controlling Tissue Parasitism and Inflammation in the Heart and Central Nervous System during Trypanosoma cruzi Infection

The role of cytokines in the control of tissue parasitism and pathogenesis of experimental Chagas' disease was investigated. Wild-type and different cytokine as well as inducible nitric oxide synthase (iNOS) knockout mice were infected with the Colombian strain of Trypanosoma cruzi, and the kinetics of tissue parasitism, inflammatory reaction, parasitemia, and mortality were determined. We demonstrate the pivotal role of the interleukin (IL)-12/interferon (IFN)-gamma/iNOS axis and the antagonistic effect of IL-4 in controlling heart tissue parasitism, inflammation, and host resistance to acute infection with T. cruzi. Further, the heart and central nervous system were shown the main sites of reactivation of T. cruzi infection in mice lacking functional genes for IFN-gamma and IL-12, respectively. Our results also show that in contrast to IFN-gamma knockout (KO) mice, splenocytes from IL-12 KO mice infected with T. cruzi produced low levels of IFN-gamma upon stimulation with antigen. Consistently, high levels of anti-T. cruzi IgG2a antibodies were detected in the sera from IL-12 KO, but not from IFN-gamma KO mice, infected with the Colombian strain of T. cruzi. Thus, our results suggest that the level of IFN-gamma deficiency is a major determinant of the site of reactivation of T. cruzi infection in immunocompromised host.

Interleukin-4 Down-regulates Both Forms of Tumor Necrosis Factor Receptor and Receptor-mediated Apoptosis, NF-κB, AP-1, and c-Jun N-Terminal Kinase: COMPARISON WITH INTERLEUKIN-13

The activity of tumor necrosis factor (TNF), a proinflammatory cytokine, is regulated by a number of other cytokines, including interleukin (IL)-4. How IL-4 regulates various activities of TNF is not fully understood. In the present report, we investigated the effect of IL-4 on the cell surface TNF receptors in human histiocytic lymphoma U-937 cells. Pretreatment of cells with IL-4 down-regulated TNF receptors in a dose- and time-dependent manner; an almost 90% decrease occurred with 10 ng/ml IL-4 treatment for 24 h. Scatchard analysis revealed that the decrease was due to receptor number and not affinity. IL-13, which shares a common receptor subunit and various biological activities with IL-4, had no effect on TNF receptors. IL-4's effect on TNF receptors was not cell type-specific, since decreases also occurred on various epithelial and T cells. Both the p60 and p80 forms of the TNF receptor were down-regulated to the same extent. Western blot showed that IL-4 induced shedding of the TNF receptors. The decrease of TNF receptors by IL-4 was accompanied by down-regulation of TNF-induced activities, including cytotoxicity, caspase-3 activation, NF-kappaB and AP-1 activation, and c-Jun N-terminal kinase induction. Wortmannin reversed the IL-4-induced TNF receptor down-regulation and all other measured cellular responses, indicating a critical role of phosphatidylinositol 3-kinase. Rapamycin also blocked the effect of IL-4-induced regulation, thus suggesting the role of p70 S6 kinase. Overall, our results suggest that TNF receptor down-regulation by IL-4 plays a critical role in the antagonistic effects of IL-4 on TNF-induced cellular responses and that this mechanism differs from that of IL-13.

Mutual inhibition by TGF-beta and IL-4 in cultured human bronchial epithelial cells.

The airway epithelial cell may play a role as an effector cell, releasing various cytokines and extracellular matrix components in immune responses, inflammation, and wound repair processes, thus contributing to cytokine "networks." The cytokines transforming growth factor (TGF)-beta and interleukin (IL)-4 are though to have pivotal roles in airway diseases, with IL-4 having proinflammatory actions and TGF-beta generally regarded to mediate repair and to attenuate immune responses. In asthma, where IL-4 and TGF-beta are thought to contribute to the inflammatory process and repair, respectively, interactions between these cytokines are likely to be of importance. Therefore, we studied the potential interaction of both cytokines by measuring IL-8 and fibronectin release by cultured human bronchial epithelial cells (HBECs). IL-4 is capable of inducing IL-8 release from HBECs. This effect of IL-4 can be blocked by the concurrent presence of the cytokine TGF-beta. In contrast, TGF-beta had a modest inconsistent stimulatory effect on IL-8 release by itself and had no effect on the IL-8 release induced by tumor necrosis factor (TNF)-alpha. An antagonistic effect of IL-4 and TGF-beta was also observed on HBEC fibronectin release. TGF-beta stimulated fibronectin release, and IL-4 was able to inhibit this. This effect was not due to a redistribution of fibronectin but appeared to be due to a true reduction in synthesis. Consistent with this, IL-4 and TGF-beta effects on IL-8 and fibronectin release were paralleled by changes in mRNA levels. The ability of TGF-beta to block IL-4-induced IL-8 release is certainly not the only mechanism to inhibit IL-8 release because dexamethasone was capable of inhibiting both TNF-alpha- and IL-4-induced release of IL-8. These results indicate that TGF-beta and IL-4 can have mutually inhibitory effects. The balance determined by this reciprocal inhibition may play an important role in regulating inflammation repair and in diseases such as asthma.

Antagonistic and additive effects of IL-4 and lnterferon-γ on human monocytes and macrophages: Effects on Fc receptors, HLA-D antigens, and superoxide production

During an immune response a multitude of lymphokines are produced which modulate the function of mononuclear phagocytes. In this study, we investigated possible additive, synergistic, or antagonistic effects of three lymphokines, IL-4 (1–100 U/ml, 0.01–1 ng/ml), interferon-γ (IFN) (1–100 U/ml) and IL-2 (30–300 U/ml) on Fc receptors (FcR1 and FcR2), complement receptors (CR3 and CR4), and HLA-D antigens (HLA-DR and HLA-DQ) on human monocytes and macrophages. Exposure of monocytes to IL-4 alone resulted in changes in the expression of all these receptors. Both FcR1 and FcR2 were downregulated in a dose-dependent manner while the expression of CR3, CR4, HLA-DR, and HLA-DQ was increased. Antagonistic effects of IL-4 and IFN were observed on FcR1 and FcR2; IL-4-induced downregulation of the FcR1 and FcR2 was inhibited by IFN, and vice versa, IFN-induced upregulation of FcR1 and FcR2 was inhibited by IL-4. Phagocytosis of particulate immune complexes (EAs) as well as production of superoxide (O 2 −) in response to EAs were inhibited by IL-4, and the inhibition was reversed by IFN. Antagonistic effects of IL-4 and IFN were also observed on CR3 and CR4 expression. Additive effects of IL-4 and IFN were on the other hand seen on HLA-DR and HLA-DQ expression as well as on O 2 − production in response to stimulation with phorbol ester (PMA). The addition of IL-2 to IL-4 and/or IFN-containing cultures had no further modulatory effect on receptor expression or O 2 − production. In vitro matured macrophages (Mφ) had a similar response pattern to IL-4 and IFN as the freshly isolated monocytes. Alveolar macrophages (AMφ), on the other hand, did not modulate FcR1 and HLA-DQ in response to IL-4, and downregulated FcR2 in response to IFN. Antagonistic effects of the two factors were only seen on CR expression. These results imply that FcR expression and function on monocytes and inflammatory macrophages may be in sensitive balance with the relative concentrations of IL-4 and IFN in the immune environment. FcRs on AMφs are less responsive to modulation by these lymphokines.

Involvement of granzyme B and perforin gene expression in the lytic potential of human natural killer cells

Natural killer (NK) cells (CD3 −) or large granular lymphocytes (LGL) spontaneously kill K562 targets but are unable to kill Daudi cells in the absence of IL-2 stimulation. IL-4 is reported to prevent or inhibit the IL-2-driven lymphokine-activated killer (LAK) generation in NK cells. Therefore, we wished to determine whether the antagonistic effect of IL-4 on IL-2-induced LAK activity might regulate the expression of genes encoding proteins involved in lysis, such as perforin, the pore-forming protein, or which are associated with lysis, such as granzymes A and B. By using in situ hybridization, we showed that, in addition to inducing LAK activity, IL-2 stimulation increased the amount of perforin and granzyme B mRNA at the single-cell level in 40 to 100% of the total CD3 − LGL cell population. In addition, our results indicated that the stimulatory effect of IL-2 can be downregulated by IL-4 for both LAK activity and granzyme B and perforin gene expression. Here again, a decrease in the amount of specific mRNA per cell was noted. These findings suggest that modulation of the lytic machinery via lymphokines might be associated with regulation of the lytic potential of NK cells.