Regulatory role of IL4 and other cytokines in the function and development of human T-cell clones

Human gastric epithelium produces IL-4 and IL-4delta2 isoform only upon Helicobacter pylori infection

Recent evidence suggests that interleukin-4 (IL-4) is related to mucosal tolerance by which an injurious immune response is prevented, suppressed or shifted to a non-injurious response. We investigated the expression of IL-4 and its splice variant isoform IL-4delta2 in gastric epithelial cells of healthy subjects and gastritis patients infected with Helicobacter pylori (H. pylori) with or without the cag pathogenicity island (cag-PAI). IL-4 and IL-4delta2 mRNAs were evaluated in microdissected gastric epithelium and in AGS cell lines co-cultured with H. pylori B128 or SS1 strains. IL-4 mRNA was consistently detected in microdissected gastric epithelial cells from healthy subjects. The IL-4 mRNA expression was low in H. pylori?infected patients, and markedly reduced in cag-PAI-positive ones. IL-4delta2 mRNA was expressed on gastric epithelium of H. pylori-infected patients, but not in healthy subjects. The IL-4delta2 expression was lower in cag-PAI-positive than in cag-PAI-negative H. pylori infected patients. AGS cells also produced IL-4 mRNA upon SS1 strain stimulation, whereas IL-4delta2 mRNA expression was detected in AGS co-cultured with either SS1 or B128 strains. An inverse correlation was documented between IL-4 and IL-4delta2 mRNA expression by microdissected gastric epithelial cells and the score of gastritis. IL-4, but not IL-4delta2, is expressed by gastric epithelium of healthy subjects, whereas IL-4delta2 and lesser IL-4 mRNA are detectable in the gastric epithelium of H. pylori-infected patients. Data suggest that gastric epithelial cells might regulate the balance between tolerance and immune response by the fine tuning of IL-4 and IL-4delta2 expression.

Cytokines and chemokines in uveitis: is there a correlation with clinical phenotype?

Uveitis is a general term for intraocular inflammation and includes a large number of clinical phenotypes. As a group of disorders, it is responsible for 10% of all registered blind patients under the age of 65 years. Immune-mediated uveitis may be associated with a systemic disease or may be localized to the eye. The pro-inflammatory cytokines interleukin (IL)-1beta, IL-2, IL-6, interferon-gamma and tumor necrosis factor-alpha have all been detected within the ocular fluids or tissues in the inflamed eye together with others, such as IL-4, IL-5, IL-10 and transforming growth factor-beta. The chemokines IL-8, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta and fractalkine are also thought to be involved in the associated inflammatory response. There have been a number of studies in recent years investigating cytokine profiles in different forms of uveitis with a view to determining what cytokines are important in the inflamed eye. This review attempts to present the current state of knowledge from in vitro and in vivo research on the inflammatory cytokines in intraocular inflammatory diseases.

Helicobacter pylori cag pathogenicity island is associated with reduced expression of interleukin-4 (IL-4) mRNA and modulation of the IL-4delta2 mRNA isoform in human gastric mucosa

Interleukin-4 (IL-4) and IL-4delta2 mRNA gastric expression was evaluated in healthy subjects and patients who did not have ulcers but were infected with Helicobacter pylori with or without the cag pathogenicity island (cag PAI). IL-4 mRNA was physiologically expressed by gastric epithelium and negatively influenced by H. pylori. Also, nonepithelial cells in the lamina propria of H. pylori-infected patients expressed IL-4 mRNA, whereas IL-4delta2 mRNA was found only in cag PAI-negative patients. Thus, gastric IL-4 takes part in the local immune response to H. pylori.

Autocrine IL-4 gene regulation at late phases of TCR activation in differentiated Th2 cells

IL-4 is a multifunctional cytokine whose secretion displays important immunomodulatory functions. Its expression is regulated at the level of transcription, and one of the main factors involved is NFAT. The IL-4-induced transcription factor Stat6 is required for the development of naive T cells into Th2 phenotype, capable of secreting IL-4. However, IL-4 production by differentiated Th2 cells is IL-4 independent; thus, it remains unclear whether Stat6 plays any role in the IL-4 expression by mature Th2 cells. We have analyzed in the Th2 clone D10.G4.1 the nuclear proteins able to bind the regulatory element P1 of the IL-4 promoter. Gel-shift assays show NFAT1 as the most abundant nuclear protein that binds to P1 after ionomycin plus PMA activation, whereas Stat6 accounts for the bulk of the P1 binding in the presence of exogenous IL-4. Reporter experiments agree with an inhibitory effect of Stat6 on the NFAT1-induced transcriptional activity directed by the P1 element. CD3 signaling leads to an early induction of NFAT1-P1 complexes correlating with a strong induction of the IL-4 gene. In later phases of CD3 activation, P1 is also bound by Stat6 and a fall in the IL-4 mRNA levels takes place. These two late events during CD3 activation were found to be sensible in experiments conducted with an anti-IL-4 Ab. These results suggest that IL-4 endogenously produced by Th2 cells under TCR triggering modulates its own expression through Stat6.

Induction of type 2 activity in adult human CD8(+) T cells by repeated stimulation and IL-4

Repeated administration or chronic presence of antigen during CD4(+) T cell activation and a cytokine milieu enriched in IL-4 favour the generation and maintenance of a T(h)2 population. However, there is little data on how these factors affect adult human CD8(+) T cell functions. We established in vitro conditions to culture purified human CD8(+) T cells, and investigated how repeated stimulation and exogenous IL-4 modulated their functions. Repeated TCR-CD3 stimulation of CD8(+) T cells increased the number of CD25-, CD30- and CD40 ligand-expressing cells, and their capacity to secrete IL-4 and IL-5. In addition, repeatedly stimulated CD8(+) T cells had cytotoxic activity and provided help to resting B cells for IgE synthesis. The presence of exogenous IL-4 during repeated stimulation further increased the number of CD25(+) and CD30(+) CD8(+) T cells, up-regulated the number of IL-5(+) cells, and increased IL-5 levels released. These observations demonstrate that repeated TCR-CD3 stimulation of normal human CD8(+) T cells favoured the growth of cells with a type 2 phenotype and that this was further amplified by the presence of IL-4. These mechanisms may be important in virus-induced lung eosinophilic inflammation in healthy subjects and virus-induced exacerbations of asthma.

Relationship between IL-4 and IL-5 mRNA expression and disease severity in atopic asthma

Atopic asthma is characterized by chronic inflammation of the bronchial mucosa in which eosinophil- and immunoglobulin E (IgE)-dependent mechanisms are believed to be prominent. Therefore, specific proeosinophilic mediators such as interleukin (IL)-5 and essential cofactors for IgE switching in B-lymphocytes such as IL-4 could play a pivotal role in asthma. However, the exact role that individual inflammatory mediators play in the development of the disease in humans is still unknown. Using semiquantitative reverse transcriptase-polymerase chain reaction amplification in bronchial biopsies from 10 atopic asthmatics, we have tested the hypothesis that IL-4 and IL-5 mRNA expression relative to beta-actin mRNA correlates with validated indicators of disease severity. IL-4 and IL-5 mRNA copies relative to beta-actin mRNA were detected in bronchial biopsies from atopic asthmatics. The numbers of IL-5 mRNA copies relative to beta-actin mRNA correlated with disease severity assessed by the Aas asthma score (r = 0.70, p = 0.01), baseline FEV1 (r = -0.94, p = 0.001), baseline peak expiratory flow rate (r = -0.77, p = 0.01), peak expiratory flow rate variability over 2 wk (r = 0.69, p = 0.028), and the histamine PC20 (r = -0.72, p = 0.018). Conversely, the numbers of IL-4 mRNA copies relative to beta-actin mRNA did not correlate with asthma severity, but they positively correlated with total serum IgE concentrations (r = -0.90, p = 0.001). Our present results support the concept that IL-5 may determine asthma clinical expression and severity, and by inference they support the development of IL-5 targeted therapies.

Responsiveness of human neutrophils to interleukin-4: induction of cytoskeletal rearrangements, de novo protein synthesis and delay of apoptosis

Interleukin-4 (IL-4) and IL-13 are cytokines that share many biological activities. We have previously demonstrated that IL-13 affects a number of neutrophil responses, and here we extend our observations to IL-4. We present, for the first time, direct evidence for the presence of functional IL-4 receptors on human neutrophils. We report that IL-4 induces RNA synthesis in a concentration-dependent manner and, based on observations of the induction of morphological cell shape changes and spreading onto glass, we demonstrate that IL-4 activates neutrophil cytoskeletal rearrangements. We further show that IL-4 is a potent activator of de novo protein synthesis in neutrophils, and we identify by microsequencing one of these proteins as the cytoskeletal protein actin. We were also able to demonstrate for the first time that actin is cleaved into at least two fragments of approximately 30 kDa (pI 5.4) and approximately 25 kDa (pI 5.0) in neutrophils. Finally, we report that IL-4 delays neutrophil apoptosis, as assessed by morphological observations from cytocentrifuge preparations, as well as by measurement of differences in staining by flow cytometry with both propidium iodide and Hoechst reagent. Taken together, we conclude that IL-4 is a more potent neutrophil agonist than previously believed. We discuss the possibility that the induction of the de novo synthesis of actin by IL-4 is related to the mechanism by which this cytokine delays apoptosis; in addition, the cleavage of this protein is likely to contribute to the apoptotic process.

Interleukin-1 favours the in vitro development of type 2 T helper (Th2) human T-cell clones

The effects exerted by interleukin-1 (IL1) on the growth and differentiation of human Th1 and Th2 cells were examined. Neither IL1 nor the IL1 receptor antagonist (IL1ra) had detectable activity toward the antigen- or anti-CD3 antibody-induced proliferative response of already established type 1 T helper (Th1) or type 2 T helper (Th2) clones. Moreover, neither exogenous IL1 addiction to, nor neutralization of, endogenously produced IL1 in bulk cultures before cloning changed the Th1-like cytokine profile of PPD-specific T-cell lines. Likewise, IL1 addition in bulk culture before cloning did not significantly affect the Th2-like cytokine profile of Der.p.I-specific T-cell lines (Dermatophagoides pteronyssinus group I). However, Der.p.I-specific T-cell lines, derived in the presence of anti-IL1 Ab, IL1ra or the M-20 IL1 inhibitor, exhibited the reduced ability to produce IL4 and an increased ability to produce interferon gamma (IFN gamma). More importantly, Der.p.I-specific T-cell lines derived in the presence of IL1ra developed into Der.p.I-specific CD4+ T-cell clones showing a Th0/Th1-like, instead of a Th0/Th2-like, cytokine profile. These data suggest that IL1 is not required for the growth of already established human Th1 or Th2 CD4+ T-cell clones and has no regulatory effects on the in vitro development of Th1-like cells, but it plays a critical role in the development of Th2-like cells.