Signals involved in the early TH1/TH2 polarization of an immune response depending on the type of antigen

Lymphocyte surface markers and cytokines are suitable for detection and potency assessment of skin-sensitizing chemicals in an in vitro model of allergic contact dermatitis: the LCSA-ly

Allergic contact dermatitis is a widespread health disorder and occupational skin disease. Hence, screening for contact-sensitizing chemicals is highly relevant to toxicology, dermatology, and occupational medicine. The use of animal tests for this purpose is constrained by ethical considerations, need for high-throughput screening, and legislation (e.g., for cosmetics in the European Union). T cell activation is the final and most specific key event of the "adverse outcome pathway" for skin sensitization and therefore a promising target for the development of in vitro sensitization assays. We present a novel in vitro sensitization assay with a lymphocyte endpoint as an add-on to the loose-fit coculture-based sensitization assay (LCSA): the LCSA-ly. While the LCSA measures dendritic cell activation, the LCSA-ly offers the option for an additional lymphocyte endpoint which can be measured concurrently. We incorporated lymphocytes in our previously established coculture of primary human keratinocytes and monocyte-derived dendritic cells and tested nine substances: five sensitizers [2,4-dinitrochlorobenzene (DNCB) 1.25-15 µmol/l, p-phenylenediamine (PPD) 15.6-125 µmol/l, 2-mercaptobenzothiazole (MBT) 50-1000 µmol/l, coumarin, and resorcinol (both: 250-1500 µmol/l)] and four non-sensitizers (monochlorobenzene, caprylic acid, glycerol, and salicylic acid (all: 125-1000 µmol/l)]. DNCB and MBT increased a subset of IL-23 receptor+/IFN-γ receptor 1 (CD119)+ lymphocytes. DNCB, PPD, and MBT enhanced a subunit of the IL-4 receptor (CD124) and a memory marker (CD44) on lymphocytes. Remarkably, DNCB, PPD, and MBT raised IL-4 concentrations in coculture supernatants while IFN-γ levels decreased, which might point to Th2 activation in vitro. Coumarin, resorcinol, and non-sensitizers did not alter any of the tested surface markers or cytokines. IL-17 was not affected by any of the substances. Relative strength of sensitizers according to lymphocyte markers was DNCB > PPD > MBT, which corresponds to earlier results from the LCSA without lymphocyte endpoint, the murine local lymph node assay, and human data. This study is the first to prove the suitability of lymphocyte surface markers for sensitization testing and potency assessment.

Oral tolerance inhibits atopic dermatitis-like type 2 inflammation in mice by modulating immune microenvironments

BACKGROUND

Oral tolerance is immune unresponsiveness induced by oral administration of innocuous antigens. Oral administration of allergens has been shown to be effective for suppressing IgE production in allergic responses. However, whether oral tolerance has a role in protection from allergic skin inflammation has not been fully investigated. Here, we evaluated the potential protective role of oral tolerance in a murine model of atopic dermatitis (AD) and investigated the underlying immunologic mechanisms.

METHODS

Mice were fed with ovalbumin (OVA) in drinking water then epicutaneously sensitized by repeated application of OVA to tape-stripped skin. Skin biopsies were analyzed for immunohistopathologic features. Levels of antibodies in sera and intestinal washes were measured by ELISA. Flow cytometry and real-time PCR analysis of the skin and mesenteric lymph nodes (MLN) were performed to investigate the immunologic effects of oral tolerance in epicutaneous (EC) sensitization-induced allergic responses.

RESULTS

Induction of oral tolerance effectively inhibited inflammatory responses provoked by EC sensitization. Tolerogenic immune mediators were significantly increased in the skin and MLN of EC-sensitized mice following induction of oral tolerance. A marked increase in Il5 and Il13 expression and infiltration of eosinophils and type 2 innate lymphoid cells (ILC2) in the skin of EC-sensitized mice were significantly inhibited by oral tolerance.

CONCLUSIONS

Oral tolerance plays a protective role in the development of AD in a murine model by modulating immune microenvironments to be more favorable for immune regulation. This modulation involves inhibition of ILC2 infiltration in skin lesions.

Is pimecrolimus cream (1%) an appropriate therapeutic agent for the treatment of external ear atopic dermatitis?

Background

In recent years, pimecrolimus 1% cream has been demonstrated to reduce symptoms of atopic dermatitis in patients when applied topically.

Material/Methods

In our study we compared the therapeutic effects of local 1% pimecrolimus to 1% hydrocortisone, and to a control group in a mouse model with atopic dermatitis in the external ear canals. Atopic dermatitis was created by application of Dinitrochlorobenzene in the external ear canals of mice. The development of atopic dermatitis was detected by clinical observation score and determination of total serum IgE levels. Pimecrolimus and hydrocortisone cream were topically applied to the external ear canal skin once a day for 14 days.

Results

There was no significant difference between the hydrocortisone and the pimecrolimus therapy groups, while there was a statistically significant difference between these 2 groups and the control group (p<0.05) Assessment of the clinical observation scoring carried out on the 14th day of therapy revealed that there was no difference between the hydrocortisone and pimecrolimus groups. Biopsies were taken on the 14^th day following treatment. Tissue samples were histologically evaluated; contact dermatitis was observed microscopically in the control group, but in the therapy groups only minimal evidence of contact dermatitis was found.

Conclusions

The results of our study reveal that the therapeutic efficacy of 1% pimecrolimus was equivalent to 1% hydrocortisone treatment in the artificially developed atopic dermatitis model in external ear canals of mice. These results clearly demonstrate that 1% pimecrolimus cream can be an effective alternative therapeutic agent in cases where steroid treatment proves to be insufficient or in cases where treatment must be discontinued due to its adverse effects.

IL-17 and IFN-gamma mediate the elicitation of contact hypersensitivity responses by different mechanisms and both are required for optimal responses

Hapten-induced contact hypersensitivity (CHS) in the skin is a delayed type cellular immune response that can be mediated by CD8(+) T cells that produce IFN-gamma or IL-17. However, mechanisms for these cytokines in the elicitation of CHS remain to be fully elucidated. In this study, we show that adoptive transfer of CHS with hapten-primed wild-type (WT) CD8(+) T cells is reduced in IFN-gammaR(-/-) or IL-17R(-/-) mice compared with WT controls. The infiltration of granulocytes and macrophages in the hapten challenged skin of IL-17R(-/-) recipients is significantly reduced whereas it is less affected in IFN-gammaR(-/-) recipients although CD8(+) T cell infiltration is inhibited in both recipients. In contrast, the activity of reactive oxidative species is significantly inhibited in IFN-gammaR(-/-) but is less affected in IL-17R(-/-) recipients. Further analysis reveals that the expression of chemokines and cytokines is differentially regulated in the hapten-challenged skin of IFN-gammaR(-/-) or IL-17R(-/-) recipients compared with WT controls. Interestingly, injection of rIL-17 in the skin induces inflammation with a high level of leukocyte infiltration whereas injection of IFN-gamma induces inflammation with a high level of reactive oxidative species. Moreover, neutralization of IL-17 in IFN-gammaR(-/-) or IFN-gamma in IL-17R(-/-) mice further suppresses the adoptive transfer of CHS by hapten-primed WT CD8(+) T cells. The study demonstrates that IFN-gamma and IL-17 mediate the elicitation of CHS by different mechanisms and that both cytokines are required for optimal responses. This outcome improves understanding of pathogenesis and provides new insights into therapeutic strategies for CHS.

House dust and forage mite allergens and their role in human and canine atopic dermatitis

This article reviews the literature regarding the role of house dust and forage mite allergens in canine atopic dermatitis. The presence of immunoglobulin E (IgE) to these mites, especially to Dermatophagoides farinae, is common in both normal and atopic dogs. Exposure of dogs to the different mites is described both in the direct environment and in the coat of animals for house dust mites and in the food for forage mites. Allergens causing allergic disease in dogs seem to be different from those in humans. Dogs seem to react to high molecular weight allergens, compared to the low molecular weight group 1 and group 2 proteases that are commonly implicated in humans with atopic diseases. Despite numerous published studies dealing with this subject, a number of questions still need to be addressed to better understand the exact role of these mites in the pathogenesis of canine atopic dermatitis and to improve the quality of the allergens used in practice.

Inhibition of scratching behavior associated with allergic dermatitis in mice by tacrolimus, but not by dexamethasone

Itching is the most important problem in many allergic and inflammatory skin diseases especially in atopic dermatitis. However, animal models for allergic dermatitis useful for the study of itching have rarely been established. We established a mouse allergic dermatitis model involving frequent scratching behavior by repeated painting with 2,4-dinitrofluorobenzene (DNFB) acetone solution onto the mouse skin, and comparatively examined the effects of tacrolimus and dexamethasone on the dermatitis and associated scratching behavior. Repeated DNFB painting caused typical dermatitis accompanied by elevated serum immunoglobulin E (IgE) and frequent scratching behavior. An apparent thickening of the epidermis and dermis, and the significant accumulation of inflammatory cells were observed. Increased interferon (IFN)-gamma mRNA expression and the induction of interleukin (IL)-4 and IL-5 mRNA expression were also observed in the skin lesion. The scratching behavior was inhibited by dibucaine and naloxone. Although tacrolimus reduced the increased expression of IFN-gamma and IL-4 mRNA, dexamethasone potently depressed that of IFN-gamma, IL-4 and IL-5 mRNA. Dexamethasone inhibited the accumulation of lymphocytes and eosinophils, although tacrolimus did not. Both drugs failed to inhibit the elevation of serum IgE levels. Tacrolimus significantly inhibited the scratching behavior that was associated with the inhibition of nerve fiber extension into the epidermis, whereas dexamethasone failed to have any effect. The mouse dermatitis model seems to be beneficial for the study of itching associated with allergic dermatitis, such as atopic dermatitis, and tacrolimus seems to exhibit an anti-itch effect through the inhibition of nerve fiber extension at least in part.

Keratinocyte-derived, CD80-mediated costimulation is associated with hapten-specific IgE production during contact hypersensitivity to TH1 haptens

Background B7-1 transgenic mice exhibit exaggerated and persistent contact hypersensitivity responses compared with normal mice. Objective Because B7-1 and B7-2 deliver different costimulatory signals to T cells during antigen presentation, the purpose of this study was to compare B7-1 and B7-2 on keratinocytes and to compare their effects on contact hypersensitivity. Methods Contact hypersensitivity was studied in transgenic mice whose keratinocytes constitutively expressed B7-1, B7-2, or no costimulatory molecules (nontransgenic mice). Results B7-1 transgenic mice, and to a lesser extent B7-2 transgenic mice, developed exaggerated ear swelling responses after sensitization and challenge with haptens such as trinitrochlorobenzene or dinitrofluorobenzene. Ear swelling responses in B7-1 transgenic mice were characterized by the presence of markedly elevated inflammatory cytokine transcripts (IL-6, TNF-alpha, and lymphotoxin beta) as well as IL-10 compared with either B7-2 or nontransgenic mice. Hapten-specific IgE was detected by ELISA in B7-1 transgenic mice but not B7-2 transgenic or nontransgenic mice. Only B7-1 transgenic mice exhibited significant immediate type ear swelling responses to the hapten trinitrochlorobenzene. In addition, their sera can passively transfer cutaneous anaphylaxis to naive C57BL/6 mice, indicating that the hapten-specific IgE was relevant to the immediate ear swelling responses. Conclusion These data suggest that keratinocyte-derived costimulation mediated by B7-1 but not B7-2 results in the emergence of T H 2-lymphocyte immune responses to T H 1 haptens. Because human keratinocytes have been noted to express B7-1-like molecules in certain inflammatory skin diseases, this model may be important in understanding the pathophysiology of T H 2-lymphocyte-mediated skin diseases such as atopic dermatitis.

T cell help is required to induce idiotypic-anti-idiotypic autoantibody network after immunization with complementary epitope 289-308aa of La/SSB autoantigen in non-autoimmune mice

Immunotherapies against autoimmune diseases have been of limited success. Preventive vaccines could be developed on the basis to abrogate unwanted immune responses to defined autodeterminants. In this study it is shown that immunization of BALB/c mice with two linear T and B cell epitopes of the human La/SSB autoantigen (spanning the regions 289-308aa and 349-364aa) and their complementary forms specified by the complementary mRNA, results in characteristic B and T cell responses. Mice immunized with the 289-308aa epitope or its complementary peptide elicited specific antibodies against both epitopes. In contrast, mice immunized with the 349-364aa epitope or its complementary peptide mounted antibody titres against the immunizing peptide only. According to these data, the 289-308aa epitope and its complementary form were capable to generate an idiotypic-anti-idiotypic response, which were cross-regulated. Peptide-specific T cell proliferation and cytokine production in vitro revealed the induction of a two-stage T helper response (Th1-->Th2 type) after immunization with either the epitope 289-308 or its complementary peptide. IgG1 was the predominant subclass after immunization with the two forms of epitopes 289-308 and 349-364, while a response of the IgG2b > IgG2a was obtained after the immunization with the complementary form of 349-364 epitope reflecting the TH2/TH1 polarization, respectively. Our data suggest that the complementary peptides of two immunodominant epitopes of human LaSSB can mimic the autoantibodies against these epitopes and establish an active idiotypic-anti-idiotypic network.

A mouse model of the atopic eczema/dermatitis syndrome by repeated application of a crude extract of house-dust mite Dermatophagoides farinae

BACKGROUND

We cultured Dermatophagoides farinae (Df), one of the most common mites in house dust and the most important allergen among natural allergens. With this material, we attempted to produce an animal model of the atopic eczema/dermatitis syndrome (AEDS).

METHODS

We cultured Df mites in high density and prepared a crude extract of Df (DfE) together with the culture medium. We applied the extract to the back skin of NC/Nga and BALB/c mice three times per week for 8 weeks.

RESULTS

In the NC/Nga group, dryness or scaling appeared on the skin, and scratching behavior increased at the second week in the DfE-treated group. Skin erosion and hemorrhage occurred at the fourth week. The epidermis thickened and deepened into the upper dermis, in which mast cells were highly accumulated, corresponding with the skin lesion of AEDS patients. Specific IgE and IgG to DfE and total IgE were elevated in the sera. Mice treated with an extract of mite culture medium did not develop skin lesions. In the BALB/c group, mice developed specific IgE and IgG to DfE, however, no typical skin lesions appeared. Mast cells in the upper dermis did not increase.

CONCLUSIONS

Repeated painting of Dermatophagoides extract produced IgE-associated AEDS-like lesions on the skin of NC mice.

Reactive oxygen species, antioxidants, and the mammalian thioredoxin system

Reactive oxygen species (ROS) are known mediators of intracellular signaling cascades. Excessive production of ROS may, however, lead to oxidative stress, loss of cell function, and ultimately apoptosis or necrosis. A balance between oxidant and antioxidant intracellular systems is hence vital for cell function, regulation, and adaptation to diverse growth conditions. Thioredoxin reductase (TrxR) in conjunction with thioredoxin (Trx) is a ubiquitous oxidoreductase system with antioxidant and redox regulatory roles. In mammals, extracellular forms of Trx also have cytokine-like effects. Mammalian TrxR has a highly reactive active site selenocysteine residue resulting in a profound reductive capacity, reducing several substrates in addition to Trx. Due to the reactivity of TrxR, the enzyme is inhibited by many clinically used electrophilic compounds including nitrosoureas, aurothioglucose, platinum compounds, and retinoic acid derivatives. The properties of TrxR in combination with the functions of Trx position this system at the core of cellular thiol redox control and antioxidant defense. In this review, we focus on the reactions of the Trx system with ROS molecules and different cellular antioxidant enzymes. We summarize the TrxR-catalyzed regeneration of several antioxidant compounds, including ascorbic acid (vitamin C), selenium-containing substances, lipoic acid, and ubiquinone (Q10). We also discuss the general cellular effects of TrxR inhibition. Dinitrohalobenzenes constitute a unique class of immunostimulatory TrxR inhibitors and we consider the immunomodulatory effects of dinitrohalobenzene compounds in view of their reactions with the Trx system.

Assessment of preferential Th1 or Th2 induction by low-molecular-weight compounds using a reverse transcription-polymerase chain reaction method: comparison of two mouse strains, C57BL/6 and BALB/c

The aim of this study was to examine whether the RT-PCR method for various Th1/Th2 cytokines is appropriate for determination of response to allergens using C57BL/6 and Balb/c mice, which are known to preferentially demonstrate Th1 and Th2 responses, respectively. To this end, both strains of mice were sensitized by skin painting with the contact allergen dinitrochlorobenzene (DNCB) or the respiratory allergen trimellitic anhydride (TMA). We used the sensitizing protocol adopted by Kimber and coworkers (Toxicology 103, 63-73, 1995). At various time points after the last application, the levels of mRNA expression for Th1-type cytokines IFN-gamma, IL-18, and IL-12p40, as well as receptor IL-18R, and the Th2-type cytokine IL-4 and the receptor ST2L, in lymph nodes were measured. The results suggest that differential expression of IL-12p40 and IL-4 mRNA after 24 h allows clear discrimination between DNCB and TMA in C57BL/6 mice, more obviously than in Balb/c mice. Furthermore, to examine this method, C57BL/6 mice were exposed to OXA, DNFB, and TNCB (Th1-predominant allergens) or PA, TDI, and MDI (Th2-predominant allergens). Elevation of IL-12p40 expression was significant with the Th1 inducers, while the level of IL-4 was higher with Th2-predominant allergens. The results of the present study demonstrate, for the first time, that differential expression of IL-12p40 and IL-4 in C57BL/6 mice may be useful as a parameter for assessing influence of contact and respiratory allergens.

Dendritic cells and their role in skin-induced immune responses

This artide gives a brief review on dendritic cells (DC) with regard to their origin, life cyde and functions. The regulation of immune responses by DC functioning as antigen-presenting cells is discussed. Special attention is given to epidermal DC, e.g. Langerhans cells. The perspectives of DC-based therapy are also mentioned.

Redox-modulated pathways in inflammatory skin diseases

Inflammatory skin diseases account for a large proportion of all skin disorders and constitute a major health problem worldwide. Contact dermatitis, atopic dermatitis, and psoriasis represent the most prevalent inflammatory skin disorders and share a common efferent T-lymphocyte mediated response. Oxidative stress and inflammation have recently been linked to cutaneous damage in T-lymphocyte mediated skin diseases, particularly in contact dermatitis. Insights into the pathophysiology responsible for contact dermatitis can be used to better understand the mechanism of other T-lymphocyte mediated inflammatory skin diseases, and may help to develop novel therapeutic approaches. This review focuses on redox sensitive events in the inflammatory scenario of contact dermatitis, which comprise for example, several kinases, transcription factors, cytokines, adhesion molecules, dendritic cell surface markers, the T-lymphocyte receptor, and the cutaneous lymphocyte-associated antigen (CLA). In vitro and animal studies clearly point to a central role of several distinct but interconnected redox-sensitive pathways in the pathogenesis of contact dermatitis. However, clinical evidence that modulation of the skin's redox state can be used therapeutically to modulate the inflammatory response in contact dermatitis is presently not convincing. The rational for this discrepancy seems to be multi-faceted and complex and will be discussed.

Role of CD4(+) T helper 2-type cells in cutaneous inflammatory responses induced by fluorescein isothiocyanate

Owing to its skin-sensitizing and fluorochromatic properties, fluorescein isothiocyanate (FITC) is employed frequently as an experimental hapten in mechanistic studies of contact allergy, particularly in the context of the role of migration and activation of Langerhans' cells. In this study we demonstrated that topical exposure of mice to FITC results in the selective development of activated lymph node cells (LNC) expressing a preferential type 2 cytokine-secretion profile, with high levels of interleukin (IL)-4 and IL-10, but low levels of interferon-gamma (IFN-gamma). Negative selection (complement depletion) identified CD4(+) T helper (Th)2-type cells as the primary source in activated LNC of the type 2 cytokines IL-4 and IL-10, whereas the low levels of IFN-gamma produced were derived exclusively from CD8(+) T cytotoxic (Tc) 1-type cells. A biphasic pattern of cutaneous inflammatory reactions was elicited by exposure to FITC, the early phase of which could be transferred passively with serum (presumably immunoglobulin E [IgE] antibody), whereas adoptive transfer experiments demonstrated that Th2-type CD4(+) cells were responsible for the delayed-type component of the dermal hypersensitivity reaction. In contrast with contact allergic reactions induced by other sensitizing haptens, which are considered to be largely Th1/Tc1-mediated immune processes regulated by Th2-type cells, these results suggest therefore that the skin lesions provoked in mice by FITC are primarily a result of the activation of Th2-type cells.

Interleukin-10 generation in atopic children following oral Lactobacillus rhamnosus GG

Oral Lactobacillus rhamnosus GG ingestion for 5 days to 4 weeks has been shown to alleviate clinical symptoms of gastrointestinal inflammation and atopic dermatitis. To determine whether oral Lactobacillus rhamnosus GG may act by generating immunosuppressive mediator in atopic children. Lactobacillus rhamnosus GG (ATCC 53103) at a daily dose of 2 x 1010 cfu was added for 4 weeks to the diets of nine children (mean age, 21 months) with atopic dermatitis. Blood and faecal samples were collected before supplementation and at early (2 weeks) and late stage (4 and 8 weeks from the beginning). The concentrations of interleukin-6 (IL-6), IL-10, IL-12, tumour necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma) in sera, as well as the production of IL-2, IL-4, IL-10 and IFNgamma in mitogen-induced peripheral blood mononuclear cells, were assessed. Secretory IgA and TNFalpha were also determined in faeces. The serum IL-10 concentration differed significantly between before, early and late samples (P < 0.001) due to the elevation of serum IL-10 in the later phase of oral Lactobacillus rhamnosus GG ingestion. The enhancement of IL-10 production in mitogen-induced cultures preceded the rise in serum IL-10. The enhanced IL-10 generation in vivo substantiates the anti-inflammatory properties of specific probiotic bacteria strains, and provides an additional reason for considering such treatments for patients with intestinal inflammation.

Allergen sensitization through the skin induces systemic allergic responses

The skin is a unique immunologic organ that acts as an interface between the external environment and the systemic immune response. As such, it may react directly with allergens that are applied epicutaneously, thereby influencing the systemic allergic response. It is well known that atopic dermatitis (frequently in association with food allergy) predates the development of asthma and allergic rhinitis by several years. The possibility that atopic dermatitis may influence the course of asthma is suggested by several interesting observations. First, children with atopic dermatitis and positive skin tests to allergens frequently have more severe asthma than asthmatic children without atopic dermatitis. Second, because total serum IgE is strongly associated with the prevalence of asthma, it raises the interesting question of whether allergen sensitization through the skin predisposes to more severe and persistent respiratory disease because of its effects on the systemic allergic response. Indeed, epicutaneous sensitization of mice to a protein antigen induces both a localized allergic dermatitis and hyperresponsiveness to methacholine, which suggests that epicutaneous exposure to antigen in atopic dermatitis may enhance the development of asthma. Finally, systemic immune activation in atopic dermatitis is supported by the observation that these patients have increased numbers of circulating activated T(H)2 cells, eosinophils, macrophages, and IgE. Many of the markers of leukocyte activation have been shown to correlate with the severity of atopic dermatitis disease. This systemic activation might facilitate local infiltration of primed T cells, eosinophils, and macrophages into the respiratory mucosa after inhalation of allergen in genetically predisposed hosts. The systemic aspects of atopic dermatitis, with an emphasis on respiratory effects, are summarized.

Conditioned suppression of contact sensitivity is independent of sympathetic splenic innervation

The present study investigated the role of sympathetic innervation of the spleen in conditioned suppression of a contact hypersensitivity (CHS) reaction. Behavioral conditioning was achieved by pairing saccharin drinking solution (conditioned stimulus, CS) with injection of cyclosporin A (CsA, 20 mg/kg; unconditioned stimulus, UCS). Four days after sensitization of the animals by application of a 5% 2,4-dinitrochlorobenzene (DNCB) to abdominal skin, the animals were challenged by applying a 1% DNCB solution to the ear. The CHS response was monitored by measuring the degree of ear swelling. Saccharin re-presentation reduced ear swelling to a magnitude that approached that achieved by CsA treatment. Histological examination demonstrated that the conditioned reduction of ear swelling was produced by a reduced leukocyte infiltration of the ear. Prior sympathetic denervation of the spleen did not alter the conditioned suppression of the CHS response. These data indicate that behavioral conditioning using CsA produces alterations of CHS that, unlike conditioned prolongation of heart allograft survival, are independent of sympathetically regulated conditioned alterations in the spleen.

IL-4 production by PBMCs on stimulation with mite allergen is correlated with the level of serum IgE antibody against mite in children with bronchial asthma

BACKGROUND

Although IL-4, IL-13, and IFN-gamma are known to affect IgE synthesis, it remains unclear which one plays the most important role in in vivo IgE synthesis in atopic patients.

OBJECTIVE

The aim of this study is to clarify the difference in importance among these cytokines in up-regulation of IgE synthesis in atopic patients.

METHODS

We measured IL-4, IL-13, and IFN-gamma production by PBMCs on stimulation with house dust mite (HDM) in 23 children, 3 to 15 years old, with bronchial asthma (BA) and analyzed the correlation with HDM-specific IgE antibody levels expressed as HDM IgE radioallergosorbent test (RAST) results.

RESULTS

The production of IL-4 and IL-13 by PBMCs on stimulation with HDM was significantly higher in children with BA than in nonatopic control subjects (IL-4, 752.9 +/- 365.9 vs 312.3 +/- 230.0 fg/mL, P <.001; IL-13, 21.9 pg/ml [<12.0-77.6] vs <12.0, P <.01). IL-4 production showed a close positive correlation with HDM IgE RAST (r = 0.71, P <.001), which was distinctly stronger than that between IL-13 production and HDM IgE RAST (r = 0.46, P <.05). IFN-gamma production was neither different between children with BA and nonatopic control subjects (7. 24 [1.54-33.90] pg/mL vs 11.2 [1.66-75.9] pg/mL) nor correlated with HDM IgE RAST levels. Essentially the same result was obtained by stimulation of PBMCs with a purified HDM major allergen Der f 1.

CONCLUSION

IL-4 is likely to be the most important cytokine in up-regulation of in vivo IgE synthesis against HDM in children with BA.