Background. In atopic asthma, activated T helper lymphocytes are present in bronchial-biopsy specimens and bronchoalveolar-lavage (BAL) fluid, and their production of cytokines may be important in the pathogenesis of this disorder. Different patterns of cytokine release are characteristic of certain subgroups of T helper cells, termed TH1 and TH2, the former mediating delayed-type hypersensitivity and the latter mediating IgE synthesis and eosinophilia. The pattern of cytokine production in atopic asthma is unknown. Methods. We assessed cells obtained by BAL in subjects with mild atopic asthma and in normal control subjects for the expression of messenger RNA (mRNA) for interleukin-2, 3, 4, and 5, granulocytemacrophage colony-stimulating factor (GM-CSF), and interferon gamma by in situ hybridization with 32P-labeled complementary RNA. Localization of mRNA to BAL T cells was assessed by simultaneous in situ hybridization and immunofluorescence and by in situ hybridization after immunomagnetic enrichment or...

Predominant TH2-like bronchoalveolar T-lymphocyte population in atopic asthma

Indoleamine 2,3-dioxygenase (IDO) is an enzyme that degrades the essential amino acid tryptophan. The concept that cells expressing IDO can suppress T-cell responses and promote tolerance is a relatively new paradigm in immunology. Considerable evidence now supports this hypothesis, including studies of mammalian pregnancy, tumour resistance, chronic infections and autoimmune diseases. In this review, we summarize key recent developments and propose a unifying model for the role of IDO in tolerance induction.

IDO expression by dendritic cells: tolerance and tryptophan catabolism.

The effects exerted on the in vitro development of antigen-specific T cell lines and T cell clones by addition or neutralization of interleukin 12 (IL-12) in lymphocyte bulk culture were examined. T cell lines specific for Dermatophagoides pteronyssinus group I (Der p I) derived in the presence of IL-12 exhibited reduced ability to produce IL-4 and increased ability to produce interferon gamma (IFN-gamma), and developed into Der p I-specific CD4+ T cell clones showing a T helper type 0 (Th0)- or Th1-, instead of Th2-, like cytokine profile. In contrast, purified protein derivative (PPD)-specific T cell lines derived in the presence of anti-IL-12 antibody exhibited an increased ability to produce IL-4 and developed into PPD-specific CD4+ T cell clones showing a Th0-, instead of Th1-, like profile. The influence of IL-12 on the cytokine secretion profile of Der p I-specific T cell lines was not prevented by addition to lymphocyte bulk cultures of anti-IFN-gamma antibody, but could be at least partially inhibited by the removal from bulk cultures of CD16+ cells. Thus, IL-12 and CD16+ cells appear to have inhibitory effects on the development of IL-4-producing cells and to play an inductive role in promoting Th1-like responses.

https://rupress.org/jem/article-pdf/177/4/1199/1103637/1199.pdf

Natural killer cell stimulatory factor (interleukin 12 [IL-12]) induces T helper type 1 (Th1)-specific immune responses and inhibits the development of IL-4-producing Th cells.

Pathogenic bacteria that penetrate the intestinal epithelial barrier stimulate an inflammatory response in the adjacent intestinal mucosa. The present studies asked whether colon epithelial cells can provide signals that are important for the initiation and amplification of an acute mucosal inflammatory response. Infection of monolayers of human colon epithelial cell lines (T84, HT29, Caco-2) with invasive strains of bacteria (Salmonella dublin, Shigella dysenteriae, Yersinia enterocolitica, Listeria monocytogenes, enteroinvasive Escherichia coli) resulted in the coordinate expression and upregulation of a specific array of four proinflammatory cytokines, IL-8, monocyte chemotactic protein-1, GM-CSF, and TNF alpha, as assessed by mRNA levels and cytokine secretion. Expression of the same cytokines was upregulated after TNF alpha or IL-1 stimulation of these cells. In contrast, cytokine gene expression was not altered after infection of colon epithelial cells with noninvasive bacteria or the noninvasive protozoan parasite, G. lamblia. Notably, none of the cell lines expressed mRNA for IL-2, IL-4, IL-5, IL-6, IL-12p40, IFN-gamma, or significant levels of IL-1 or IL-10 in response to the identical stimuli. The coordinate expression of IL-8, MCP-1, GM-CSF and TNF alpha appears to be a general property of human colon epithelial cells since an identical array of cytokines, as well as IL-6, also was expressed by freshly isolated human colon epithelial cells. Since the cytokines expressed in response to bacterial invasion or other proinflammatory agonists have a well documented role in chemotaxis and activation of inflammatory cells, colon epithelial cells appear to be programmed to provide a set of signals for the activation of the mucosal inflammatory response in the earliest phases after microbial invasion.

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A distinct array of proinflammatory cytokines is expressed in human colon epithelial cells in response to bacterial invasion.

Human TH1 and TH2 subsets: doubt no more

Lymphokine secretion profiles were studied of human allergen-specific CD4+ T lymphocyte clones (TLC). To this aim, panels of house dust mite Dermatophagoides pteronyssinus (Dp)-specific TLC were generated from two atopic Dp-allergic patients, suffering from severe atopic dermatitis (AD1) and allergic asthma (AD2), respectively, and from a non-atopic individual (NAD). From AD1 additional TLC were cloned specific for tetanus toxoid or Candida albicans, both Ag that were not relevant for the atopic state of this patient. Secretion of IL-2, IL-4, and IFN-gamma was determined after specific stimulation of these TLC, using autologous monocytes as APC. With respect to the production of IL-4 and IFN-gamma, clearly distinct profiles were observed. All Dp-specific TLC from both atopic donors produced IL-4 but not IFN-gamma, whereas the Dp-specific TLC from NAD, as well as the tetanus toxoid- and C. albicans-specific TLC from AD1, all produced IFN-gamma but not or small quantities of IL-4. Most TLC from all panels produced IL-2. These lymphokine profiles were consistent for at least 3 days and were neither dependent on the dose of allergen nor on the atopic or nonatopic state of the donor of APC. The functional consequence of these restricted lymphokine profiles was stressed by the observation that, whereas Dp-specific TLC from AD1 and AD2 supported in vitro IgE production, this support could be abrogated by a Dp-specific TLC from NAD. The present results suggest that CD4+ T lymphocytes that produce IL-4, but not IFN-gamma, occur in high frequencies in the allergen-specific T cell repertoires of atopic donors, which may have important implications for the pathomechanism of atopic disease.

Evidence for compartmentalization of functional subsets of CD2+ T lymphocytes in atopic patients

Eight representative T lymphocyte clones (TLC) randomly selected from previously described panels of CD4+ housedust mite Dermatophagoides pteronyssinus (Dp)-specific TLC from atopic and nonatopic donors were studied in more detail in a comparative investigation. The TLC from the atopic donors closely resembled murine type 2 Th (Th2) cells by secreting substantial IL-4, IL-5, IL-6, TNF-alpha, and granulocyte-macrophage (GM)-CSF, minimal IFN-gamma, and relatively little IL-2. In contrast, the nonatopic's TLC resembled murine type 1 Th (TH1) cells by secreting substantial IFN-gamma, IL-2, TNF-alpha, and GM-CSF, no IL-4, and little IL-5. A difference with murine Th1 cells was their additional secretion of IL-6. These cytokine profiles were consistent upon stimulation via different activation pathways including stimulation with specific Dp Ag, mitogenic lectins, and antibodies to CD2, CD3, or CD28. The observed differences in IL-2 secretion, however, were most evident upon stimulation with anti-CD28. If TLC cells were cultured with highly purified B cells and stimulated with anti-CD3 in the absence of exogenous IL-4, IgE synthesis was induced only in cultures with the atopics' Th2 clones, which could be completely abrogated by anti-IL-4. The mere presence of exogenous rIL-4, however, did not result in IgE synthesis, nor did unstimulated TLC cells alone. But if unstimulated TLC cells (that proved not to secrete detectable amounts of cytokines) were added together with rIL-4, again IgE synthesis was induced only in cultures with the atopics' Th2 clones, suggesting the involvement of an additional, as yet unidentified accessory helper function of the atopics' Th2 clones for IgE induction. Unstimulated Th2 clones showed a significantly higher expression of CD28 than the Th1 clones, but three days after stimulation, CD28 expression was elevated to comparable levels on both subsets. When added to B cells at this time point, together with rIL-4 and anti-IFN-gamma, still only the atopics' Th2 clones supported IgE synthesis, arguing against a role for CD28 in this accessory helper function. Whereas the atopics' Th2 clones were excellent helper cells for IgE induction, a unique property of the nonatopic's Th1 clones was their cytolytic activity toward autologous APC which could be induced by specific Dp Ag and by anti-CD3. The present data provide clear evidence for the existence of Th1 and Th2 cells in man.

Human atopen-specific types 1 and 2 T helper cell clones

Panels of CD4+CD8- T lymphocyte clones (TLC), specific for house dust mite Dermatophagoides pteronyssinus (Dp) proteins, were generated from the peripheral blood of an atopic Dp-allergic donor (AD), suffering from severe atopic dermatitis, and a histocompatible non-atopic donor (NAD). We studied the diversity of TLC within these two panels in search for the possible occurrence of dominant clone types with properties that might be characteristic for the atopic or non-atopic state. TLC with specificities for at least four different Dp proteins were found within the panel from AD "L" and for at least three different Dp proteins within the panel from NAD "K". In addition, both panels showed a considerable but comparable restriction diversity within HLA-DR. Despite the diversity within the panels, all Dp-specific TLC from AD were found to produce IL 4, after HLA class II-restricted Dp-specific stimulation, whereas the TLC from NAD produced no or only minimal amounts of this lymphokine. Only supernatants from stimulated AD TLC could induce IgE secretion by B cells from NAD. Conclusively, these observations do not give evidence for the occurrence of an abnormal Dp-specific T cell repertoire in AD, but rather suggest aberrant secretion of the IgE-inducing lymphokine IL 4 by CD4+ Dp-specific T cells from AD.

Comparison of diversity and function of house dust mite-specific T lymphocyte clones from atopic and non-atopic donors

Lung epithelial cells contribute to local inflammation by the production of pro-inflammatory mediators like interleukin (IL)-8 and IL-6. Although their production depends on gene transcription, previous studies showed that post-transcriptional mechanisms modulate IL-8 and IL-6 production. Human lung epithelial cells turn from normoresponsive into hyperresponsive IL-8– and IL-6–producing cells when their IL-8 and IL-6 mRNA degradation is reduced. We hypothesized that IL-17, a mediator predominantly released by memory T cells and present in airways of individuals with asthma, would modulate rather than induce IL-8 and IL-6 production by both human lung epithelial cells and fibroblasts. We show here for both cell types that IL-17 was a weak stimulus of IL-8 and IL-6 production, but markedly enhanced IL-8 and IL-6 responses to another stimulus, such as tumor necrosis factor-α. This modulatory effect of IL-17 was paralleled by a reduced IL-8 and IL-6 mRNA degradation, with no effect on IL-8 and IL-6 gene trans...

https://www.atsjournals.org/doi/pdf/10.1165/rcmb.2005-0022OC

Interleukin-17 Induces Hyperresponsive Interleukin-8 and Interleukin-6 Production to Tumor Necrosis Factor-α in Structural Lung Cells

Respiratory viral infections increase inflammatory responses to concurrent or secondary bacterial challenges, thereby worsening disease outcome This potentiation of inflammation is explained at least in part by IFN-gamma promoting increased sensitivity to TNF-alpha and LPS We sought to determine whether and, if so, how IFN-gamma can modulate proinflammatory responses to TNF-alpha and LPS by epithelial cells, which are key effector cells in the airways Preincubation of airway epithelial-like NCI-H292 cells with IFN-gamma resulted in a hyperresponsive IL-6 and IL-8 production to TNF-alpha and LPS The underlying mechanism involved the induction of indoleamine 2,3-dioxygenase, which catabolized the essential amino acid, tryptophan Depletion of tryptophan led to stabilization of IL-6 and IL-8 mRNA and increased IL-6 and IL-8 responses, whereas supplementing tryptophan largely restored these changes This novel mechanism may be implicated in enhanced inflammatory responses to bacterial challenges following viral infection

Mieke Snoek

Papers

Evidence for compartmentalization of functional subsets of CD2+ T lymphocytes in atopic patients

Human atopen-specific types 1 and 2 T helper cell clones

Comparison of diversity and function of house dust mite-specific T lymphocyte clones from atopic and non-atopic donors

Interleukin-17 Induces Hyperresponsive Interleukin-8 and Interleukin-6 Production to Tumor Necrosis Factor-α in Structural Lung Cells

IFN-gamma amplifies IL-6 and IL-8 responses by airway epithelial-like cells via indoleamine 2,3-dioxygenase.