Dendritic cell phenotype in severe asthma reflects clinical responsiveness to glucocorticoids.

BACKGROUND: Subsets of patients with severe asthma remain symptomatic despite prolonged, high-dose glucocorticoid therapy. We hypothesized that the clinical glucocorticoid sensitivity of these asthmatics is reflected in differences in peripheral blood dendritic cell subsets. OBJECTIVE: To compare peripheral blood leucocyte populations using flow cytometry at baseline and after 2 weeks of systemic glucocorticoid (steroid) treatment to identify immunological differences between steroid-sensitive (SS) and steroid-resistant (SR) asthmatics. METHODS: Adult severe asthmatics (SS n = 12; SR n = 23) were assessed for their response to 2 weeks of therapy with oral prednisolone. Peripheral blood was obtained before and after therapy and stained for lymphocyte (CD3, CD19, CD4, CD8 and Foxp3) and dendritic cell markers (Lineage negative [CD3, CD14, CD16, CD19, CD20, CD56], HLA-DR+, CD304, CD11c, ILT3 and CD86). RESULTS: A higher median frequency of myeloid DCs (mDCs) but not plasmacytoid DCs (pDCs) was observed in the blood of SR as compared to SS asthmatics (P = .03). Glucocorticoid therapy significantly increased median B cell, but not T cell numbers in both cohorts, with a trend for increased numbers of Foxp3+ Tregs in SS (P = .07), but not SR subjects. Oral prednisolone therapy significantly reduced the median numbers and frequencies of total DCs and pDCs in both SS and SR asthmatics. Interestingly, the expression of HLA-DR and ILT3 was also reduced on pDCs in all patients. In contrast, therapy increased the median frequency of mDCs in SS, but reduced it in SR asthmatics. CONCLUSIONS: Myeloid DC frequency is elevated in SR compared with SS asthmatics, and mDC shows a differential response to oral prednisolone therapy.

Potential role of interleukin-10-secreting regulatory T cells in allergy and asthma.

Allergic diseases are caused by aberrant T-helper-2 immune responses in susceptible individuals. Both naturally occurring CD4(+)CD25(+) regulatory T cells and inducible populations of antigen-specific interleukin-10-secreting regulatory T cells inhibit these inappropriate immune responses in experimental models. This article discusses the evidence that regulatory T-cell function might be impaired in allergic and asthmatic disease and that certain therapeutic regimens might function, at least in part, to promote regulatory T-cell generation. Current research strategies seek to exploit these observations to improve the generation of allergen-specific regulatory T-cell populations with the potential to provide the safe and long-term alleviation of disease symptoms.

Vitamin D deficiency induces Th2 skewing and eosinophilia in neonatal allergic airways disease.

BACKGROUND: Associations between vitamin D status and childhood asthma are increasingly reported, but direct causation and mechanisms underlying an effect remain unknown. We investigated the effect of early-life vitamin D deficiency on the development of murine neonatal allergic airways disease (AAD). METHODS: In utero and early-life vitamin D deficiency was achieved using a vitamin D-deficient diet for female mice during the third trimester of pregnancy and lactation. Offspring were weaned onto a vitamin D-deficient or vitamin D-replete diet, and exposure to intranasal house dust mite (HDM) or saline was commenced from day 3 of life for up to 6 weeks, when airway hyper-responsiveness (AHR), airway inflammation and remodelling were assessed. RESULTS: Neonatal mice that had in utero and early-life vitamin D deficiency had significantly increased pulmonary CD3(+) CD4(+) T1ST2(+) cells and reduced CD4(+) IL-10(+) cells. This effect was enhanced following HDM exposure. AHR in HDM-exposed mice was unaffected by vitamin D status. Introduction of vitamin D into the diet at weaning resulted in a significant reduction in serum IgE levels, reduced pulmonary eosinophilia and peri-bronchiolar collagen deposition. CONCLUSION: Peri-natal vitamin D deficiency alone has immunomodulatory effects including Th2 skewing and reduced IL-10-secreting T regulatory cells, exaggerated with additional allergen exposure. Vitamin D deficiency in early life does not affect AHR, but contributes to disease severity with worse eosinophilic inflammation and airway remodelling. Importantly, supplementation with vitamin D improves both of these pathological abnormalities.

A randomized placebo-controlled trial of rush preseasonal depigmented polymerized grass pollen immunotherapy.

BACKGROUND: Specific subcutaneous immunotherapy (SCIT) for seasonal rhinoconjunctivitis with unmodified allergen extracts is effective, but limited by risk of side-effects and involves treatment over 3 years. We examined a depigmented polymerized grass pollen extract for immunogenicity and for clinical efficacy in a rush preseasonal regimen. METHODS: Depigmented polymerized grass pollen extract was tested for proliferation and cytokine production by peripheral blood mononuclear cells. A prospective, double-blind, placebo-controlled trial of 195 grass pollen allergic patients treated with preseasonal rush immunotherapy using depigmented polymerized allergenic extract of mixed grass pollen was performed over 2 years. Primary outcome was combined symptom and medication score (SMS) during the peak of the second grass pollen season. Secondary outcomes included combined score over the whole season, during the first grass pollen season, individual symptom and medication scores, quality of life, well days/hell days and responder analysis. Adverse events were classified using the EAACI scale. Grass pollen-specific IgE and IgG4 were measured before and during treatment. RESULTS: Depigmented polymerized extract stimulated dose-dependent T-cell proliferation and cytokine production. Patients treated with preseasonal SCIT showed improved combined scores during peak season at year 2 (median 3.93, interquartile range 0.77-6.27 vs median 5.86 for placebo, 3.11-8.36, P < 0.01). Most secondary outcomes were significantly better for active treatment. Side-effects were minimal, with no grade 3 or 4 reactions. CONCLUSIONS: Depigmented polymerized grass pollen extract is immunogenic and clinically effective in rush preseasonal SCIT. This form of immunotherapy may be an attractive option for some patients.

T cells producing the anti-inflammatory cytokine IL-10 regulate allergen-specific Th2 responses in human airways.

BACKGROUND: Murine models suggest a critical functional role for the anti-inflammatory cytokine IL-10 in local regulation of allergic airways inflammation. There is little corresponding information on human airway cells. This study aimed to investigate whether local IL-10 production regulates responses by respiratory mucosal leucocytes isolated from nasal polyps. MATERIALS AND METHODS: Nasal polyp tissue was harvested from 24 patients sensitised to aeroallergens with chronic rhinitis and polyposis undergoing routine polypectomy. Cells were isolated by matrix proteolysis. Cytokine production by polyp cells was determined by cytometric bead array (CBA) and intracellular cytokine analysis. Surface marker expression by polyp cells was determined by flow cytometry. RESULTS: Allergen stimulation significantly enhanced production of IL-10, but not IL-5 or IFN-γ by nasal polyp cell suspensions. Under the same conditions, neutralisation of IL-10 significantly increased allergen-specific IL-5 and IFN-γ production by nasal polyp cells. Cell depletion experiments showed that T cells themselves were primarily responsible for IL-10 production or for inducing its production by other cells. Intracellular cytokine staining confirmed production of IL-10 in the absence of IL-2 production by T cells in response to allergen. CONCLUSION: T cells within the human respiratory mucosa produce IL-10, which is capable of inhibiting pro-inflammatory Th2 and Th1 cytokine production in an antigen-specific fashion.

Platelet-derived interleukin 1 induces human endothelial adhesion molecule expression and cytokine production.

Interleukin 1 (IL-1) plays a central role in the regulation of the body's response to infectious and inflammatory stimuli. Recent evidence has shown that human platelets express a cell associated form of this proinflammatory cytokine very rapidly following activation. Since one of the earliest events in inflammation is frequently the rapid adhesion of platelets to injured endothelium, it was of interest to determine whether platelets express IL-1 in a functionally relevant form that can alter the phenotype of human endothelial cells in vitro. Thrombin activated platelets induced significant expression of the adhesion molecule intercellular adhesion molecule 1, as well as secretion of the IL-1 inducible cytokines IL-6 and granulocyte macrophage colony stimulating factor by cultured human umbilical cord and saphenous vein endothelial cells. This was inhibited by prior treatment of the platelets with antibody specific for IL-1. These results suggest that platelet delivered IL-1 might initiate and regulate some of the earliest phases of the inflammatory response. An additional observation of interest was differential induction of endothelial leucocyte adhesion molecule 1 by activated platelets on saphenous vein but not umbilical vein but not umbilical vein endothelial cells, which suggests functional heterogeneity of the endothelial cells.

A novel technique to explore the functions of bronchial mucosal T cells in chronic obstructive pulmonary disease: application to cytotoxicity and cytokine immunoreactivity.

Bronchial mucosal CD8(+) cells are implicated in chronic obstructive pulmonary disease (COPD) pathogenesis, but there are few data on their functional properties. We have developed a novel technique to outgrow these cells from COPD patients in sufficient numbers to examine effector functions. Endobronchial biopsies from 15 COPD smokers and 12 ex-smokers, 11 control smokers and 10 non-smokers were cultured with anti-CD3/interleukin (IL)-2 ± IL-15. Outgrown CD3(+) T cells were characterized in terms of phenotype (expression of CD4, 8, 25, 28, 69 and 56), cytotoxicity and expression of COPD-related cytokines. Compared with IL-2 alone, additional IL-15 increased the yield and viability of biopsy-derived CD3(+) T cells (12-16-day culture without restimulation) without alteration of CD4(+) /CD8(+) ratios or expression of accessory/activation molecules. Biopsy-derived T cells, principally CD8(+)/CD56(+) cells, exhibited statistically significantly greater cytotoxic activity in current or ex-smokers with COPD compared with controls (P < 0·01). Elevated percentages of CD8(+) T cells expressed interferon (IFN)-γ, tumour necrosis factor (TNF)-α and IL-13 (P < 0·01) in current COPD smokers compared with all comparison groups. It is possible to perform functional studies on bronchial mucosal T cells in COPD. We demonstrate increased CD8(+)CD56(+) T cell cytotoxic activity and expression of remodelling cytokines in smokers who develop COPD.

Role of cysteinyl leukotrienes in human allergen-specific Th2 responses induced by granulocyte macrophage-colony stimulating factor.

BACKGROUND: The pro-inflammatory cytokine, granulocyte macrophage-colony stimulating factor (GM-CSF), which is elevated in the lungs of atopic asthmatic patients, has been shown to enhance major histocompatibility class II expression of alveolar macrophages (AM). We hypothesized that exposure of AM and monocytes from atopic asthmatic patients to GM-CSF would enhance their antigen presenting function, and investigated putative mechanisms for this effect. METHODS: Alveolar macrophages were purified from bronchoalveolar lavage by plastic adherence. Monocytes and CD4(+) T cells were purified from peripheral blood by magnetic bead separation. Antigen-presenting cell (APC) were pretreated with GM-CSF, pulsed with allergen and cocultured with autologous T cells. T-cell proliferation was determined by tritiated thymidine incorporation and cytokine production by enzyme-linked immunosorbent assay. RESULTS: Exposure of allergen-pulsed AM and peripheral blood monocytes to GM-CSF significantly increased allergen-specific T-cell proliferation and T helper 2 (Th2) cytokine production. The enhanced response was dependent on costimulation by CD86, but not CD80. Inhibition of the 5-lipoxygenase pathway abrogated GM-CSF-mediated upregulation by monocytes of allergen-specific interleukin-5 (IL-5) and IL-13 cytokine production. Blocking of the cysteinyl leukotriene receptor 1 (cysLT(1)) receptor by a specific receptor antagonist inhibited allergen-specific IL-5 production in response to GM-CSF pretreatment. CONCLUSION: Exposure to GM-CSF enhanced the capacity of human APC from atopic asthmatic patients to induce allergen-specific Th2 responses by a mechanism involving cysLT. Novel immunotherapies, targeting production of GM-CSF or its actions on APC have the potential, therefore, to prove beneficial in treatment of patients with inflammatory airway disease.

Human spleen cells mediating natural killing: altered natural cytotoxicity of spleen effector cells from patients with carcinoma.

Spleen cells from eight patients with abdominal carcinoma and six patients undergoing major surgery for a variety of disease entities were assayed for natural cytotoxicity towards 51Cr-labelled K 562 target cells. Patients with abdominal cancer were shown to have relatively weak splenic natural cytotoxicity compared with the reactivity of effector cells from non-carcinoma patients. Nylon wool non-adherent spleen effector cells from cancer patients showed reduced cytolytic capacity compared with effector cells prepared from the spleens of other patients or peripheral blood mononuclear cells (PBMC) obtained from healthy individuals, whereas the splenic reactivity of non-cancer patients showed the same nylon wool separation profile as PBMC, high cytolytic activity being associated with nylon wool non-adherent effector cells. Splenic effector cell cytotoxicity from cancer and non-cancer patients was enhanced following exposure to human interferon, and inhibited by treatment with cholera toxin and simple sugars. Furthermore, fractionation of spleen cells on Percoll discontinuous density gradients demonstrated natural cytotoxic activity to reside predominantly in the low density cell fractions, similar to that found with NK cells from peripheral blood. Thus the properties described here for human cytotoxic spleen cells are similar to those described for peripheral blood NK cells, suggesting these two effector cell populations to be closely related, if not identical.

T regulatory cells and the control of allergic disease.

Allergic diseases are caused by the induction of T helper (Th)2 cells and IgE responses specific for common environmental antigens (allergens) in susceptible individuals. There is increasing interest in the role of both naturally occurring and induced regulatory T cell (Treg) populations in preventing these inappropriate immune responses and the underlying sensitisation to allergens. Current evidence suggests that Tregs may actively prevent Th2 responses to allergens occurring in healthy non-atopic individuals and that their function may be impaired in allergic patients. Evidence that existing therapies may act by modulating Treg function is reviewed. Future research aims to understand the mechanisms involved in the generation and function of allergen-specific Tregs. A primary aim is to promote the development of optimised therapeutic regimens with the capacity to provide long-lasting, allergen-specific, inhibitory mechanisms at the time and site of allergen challenge.

Regulation of antigen-presentation-I. IFN-gamma induces antigen-presenting properties on B cells.

B cells require activation to efficiently present Ag to T cells. In agreement with this earlier observation we show that live, mitomycin C-treated B cells, but not B cells fixed in paraformaldehyde, stimulated the growth of allogeneic T cells in the primary MLR. However, if B cells were cultured with anti-Ig antibodies and IFN-gamma before fixation they acquired excellent T cell stimulatory activity. Neither reagent alone conferred this novel co-stimulatory function on the B cell surface. The activity induced by both stimuli was not attributed to an increase expression of class II-MHC molecules or IL-1. IL-2 or IL-4, in combination with anti-Ig, also induced B cell stimulatory activity, but were less effective than IFN-gamma. TNF failed to stimulate B cells, but synergized with IFN-gamma in the induction of this activity. These studies therefore demonstrate an important role for lymphokines in modulating B cell Ag-presenting activity as well as the acquisition by B cells of a novel co-stimulatory surface activity.

Activation and proliferation signals in mouse B cells. II. Evidence for activation (G0 to G1) signals differing in sensitivity to cyclosporine.

We have previously shown that cyclosporine (CS) selectively inhibits polyclonal activation of B cells by anti-Ig antibodies but not by lipopolysaccharide (LPS). Here we extend these results using a two-stage B cell culture system in which cells from either CBA/N or normal mice are activated to enter G1 by anti-Ig, and are then stimulated to proliferate by LPS. In this system CS blocks an event that occurs within 4 h after initial activation, i.e. prevents entry of B cells into G1. Phorbol myristic acetate also induces some CBA/N B cells to enter G1. However, activation of B cells by this agent is resistant to inhibition by CS. These data suggest that there are two biochemically distinct mechanisms for driving resting B cells into G1. A hypothesis to explain these results is presented.

Activation and proliferation signals in mouse B cells. IV. Concanavalin A stimulates B cells to leave G0, but not to proliferate.

Concanavalin A (Con A), in solution, induces mouse T cells, but not B cells, to proliferate. However, lectin concentrations which were optimal for the T cell response induced purified B cells to depolarize, to enlarge, and to display increased levels of Ia antigens. Furthermore, culturing B lymphocytes with Con A for 24 hr caused the cells to synthesize DNA more rapidly in response to subsequent stimulation by lipopolysaccharide, or anti-immunoglobulin antibodies. This priming effect did not appear to require either T cells or accessory cells. It was therefore concluded that Con A activates resting B lymphocytes, i.e. stimulates them to enter the cell cycle, even though it does not induce B cells to divide.

Effects of tumour promoter phorbol myristate acetate on mouse lymphocytes: selective inhibition of B cell activation by mitogens and antigens.

The effect of the tumour promoter phorbol myristate acetate (PMA) on the responses of mouse lymphocytes to various stimuli was studied in vitro. Nanomolar concentrations of PMA inhibited B cell proliferation induced by lipopolysaccharide and by anti-Ig antibodies, and the polyclonal antibody response to lipopolysaccharide. Specific antibody responses to both T-dependent and T-independent antigens were similarly affected. In marked contrast, T cell proliferation elicited by various mitogens was 10- to 1000-fold more resistant to inhibition. Cell fractionation experiments suggest that the effects on B cell responses are the results of a direct anti-proliferative effect of PMA on responding B lymphocytes.

Cell-cycle control in lymphocyte stimulation.

Discussion of lymphocyte mitogenesis often gives the impression that the process, once started, continues inexorably. It does not. Here Gerry Klaus and Catherine Hawrylowicz discuss the arrest points now known to occur in the division cycle of T and B lymphocytes and the signals required for progression through the cycle.

T helper cell subsets require the expression of distinct costimulatory signals by antigen-presenting cells.

We examined the ability of macrophages and B cells to function as antigen-presenting cells (APCs) for murine TH1 and TH2 cloned T helper cell lines. Antigen presented by concanavalin A-elicited peritoneal macrophages or resting splenic B cells stimulated antigen-dependent proliferation of both T helper subsets. Paraformaldehyde fixation of the APCs following different conditions of activation indicated differential requirements for costimulatory signals by TH1 and TH2 cells. TH2 proliferative responses were strictly dependent on APC expression of IL-1. TH1 proliferation was dependent on APC expression of a non-IL-1 costimulatory signal present on freshly isolated macrophages and on splenic B cells activated with anti-immunoglobulin plus interferon gamma.

Dexamethasone up-regulates granulocyte-macrophage colony-stimulating factor receptor expression on human monocytes.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) are weak inducers of major histocompatibility complex (MHC) class II expression on purified human blood monocytes. The glucocorticoid dexamethasone synergizes with GM-CSF or IL-3 for the upregulation of HLA-DR, -DP and -DQ antigen mRNA and cell-surface expression by these cells. The purpose of the present study was to address the mechanism of dexamethasone action. We demonstrate that the capacity of dexamethasone to up-regulate GM-CSF-induced MHC class II expression correlates with the capacity to up-regulate GM-CSF receptor, but not the interferon-gamma (IFN-gamma) receptor, in a highly dose-dependent manner on monocytes. Although dexamethasone induces GM-CSF receptor expression, it does not confer responsiveness to IL-5, a cytokine that shares a common chain of its heterodimeric cytokine receptor signalling molecule with IL-3 and GM-CSF. Three other steroid hormones, beta-oestradiol, vitamin D3 and dehydroepiandosterone (DHEA), were also tested for their capacity to up-regulate MHC class II expression. All three mediators failed to enhance MHC class II expression or GM-CSF receptor expression on the surface of human monocytes. These experiments suggest that dexamethasone may act to up-regulate GM-CSF-induced MHC class II antigen expression on monocytes by up-regulating cytokine receptor expression.

Synergy between dexamethasone and interleukin-5 for the induction of major histocompatibility complex class II expression by human peripheral blood eosinophils.

The hematopoietic growth factors interleukin-3 (IL-3), IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) regulate the survival, maturation, and activation of eosinophils. Corticosteroids in contrast have a negative effect both on the hematopoietic process and the function of eosinophils. We have unexpectedly observed synergy between IL-5 and glucocorticoids such as dexamethasone and hydrocortisone for induction of the MHC class II antigens HLA-DR and HLA-DP on eosinophils isolated from human blood. Similarly glucocorticoids enhanced GM-CSF and IL-3, but not interferon gamma (IFN gamma), induced expression of these antigens. Expression of a third MHC class II molecule, HLA-DQ, was not induced on eosinophils by any of the cytokines alone, but in one of three donors tested, IL-3 plus dexamethasone induced high levels of expression. Although cytokine-induced expression of the accessory molecule intercellular adhesion molecule 1 (ICAM-1) was partially inhibited by glucocorticoids, cytokine- and dexamethasone-treated eosinophils presented antigen more efficiently to a hemagglutinin peptide-specific T-cell clone than eosinophils treated with cytokine alone. These results highlight a potential new role for endogenous or exogenous glucocorticoid hormones in enhancing MHC class II expression by eosinophils.

Synergism of glucocorticoids with granulocyte macrophage colony stimulating factor (GM-CSF) but not interferon gamma (IFN-gamma) or interleukin-4 (IL-4) on induction of HLA class II expression on human monocytes.

Peripheral blood monocytes from up to 13 normal donors were stimulated with the cytokines interferon gamma (IFN-gamma), interleukin 4 (IL-4) and granulocyte macrophage-colony stimulating factor (GM-CSF) in the presence or absence of dexamethasone (Dex), and the effects on HLA class II (HLA-DR, DP and DQ) expression studied. Dex markedly augmented HLA-DR, DP and DQ levels induced by GM-CSF, in all samples tested. Particularly striking were the effects on HLA-DQ expression, since stimulation with a combination of Dex and GM-CSF induced markedly higher levels of HLA-DQ antigen than stimulation with IFN-gamma. Northern blot analysis of samples treated for 40 hours with Dex and GM-CSF indicated that levels of DR alpha, DP alpha and DQ alpha mRNA were also increased. In contrast, despite variation between individual donors, in general Dex weakly inhibited both constitutive and IFN-gamma- or IL-4-induced HLA-DR expression. Variability in the responsiveness of monocytes purified from individual donors to each cytokine was also observed. GM-CSF was less potent than IFN-gamma and IL-4, enhancing HLA class II expression in only seven of 13 donors tested, whereas in the presence of Dex all donors responded to GM-CSF. The differential effects of glucocorticoids in vitro suggest that these cytokines induce HLA class II expression by different mechanisms.

Activation and proliferation signals in mouse B cells. VI. Anti-Ig antibodies induce dose-dependent cell cycle progression in B cells.

Recent studies from several laboratories have shown that the concentrations of anti-immunoglobulin antibodies required to induce B lymphocytes to synthesize DNA are quite different from those needed to activate these cells, i.e. to cause resting B cells to leave G0. The present experiments examine this difference in detail. Thus, stimulation of DNA synthesis in mouse B cells requires prolonged (greater than 30 hr) exposures to high (greater than or equal to 10 micrograms/ml) concentrations of soluble F(ab')2 fragments of rabbit anti-Ig antibodies. However, as little as 50 ng/ml antibody caused B cells to enlarge, to express increased levels of Ia antigens, and to become primed to synthesize DNA more rapidly in response to restimulation with mitogenic concentrations of anti-Ig. The results of kinetic experiments suggested that the 'distance' that cells progress from G0 towards S depends not only on the time of exposure to anti-Ig, but also on its concentration. Concentrations of antibody less than 1 microgram/ml did not induce detectable RNA synthesis, and hence do not drive cells into the G1 phase of the cell cycle. Instead, under these conditions, B cells appear to enter a transitional, primed state (which has been termed GIT). This may well reflect the state into which T-dependent antigens drive resting B cells.