Reduced interferon-gamma (IFN-gamma) secretion with increased IFN-gamma mRNA expression in atopic dermatitis: evidence for a post-transcriptional defect

Impact of Skin Exposure to Benzo[a]pyrene in Rat Model: Insights into Epidermal Cell Function and Draining Lymph Node Cell Response

The skin is a direct target of the air pollutant benzo[a]pyrene (BaP). While its carcinogenic qualities are well-studied, the immunotoxicity of BaP after dermal exposure is less understood. This study examines the immunomodulatory effects of a 10-day epicutaneous BaP application, in environmentally/occupationally relevant doses, by analyzing ex vivo skin immune response (skin explant, epidermal cells and draining lymph node/DLN cell activity), alongside the skin's reaction to sensitization with experimental hapten dinitrochlorobenzene (DNCB). The results show that BaP application disrupts the structure of the epidermal layer and promotes immune cell infiltration in the dermis. BaP exposure led to oxidative stress in epidermal cells, characterized by decreased reduced glutathione and increased AHR and Cyp1A1 expression. Production and gene expression of proinflammatory cytokines (TNF, IL-1β) by epidermal cells decreased, while IL-10 response increased. Decreased spontaneous production of IFN-γ and IL-17, along with unchanged IL-10, was observed in DLC cells, whereas ConA-stimulated production of these cytokines was elevated. Local immunosuppression caused by BaP application seems to reduce the skin's response to an additional stimulus, evidenced by decreased effector activity of DLN cells three days after sensitization with DNCB. These findings provide new insight into the immunomodulatory effects and health risks associated with skin exposure to BaP.

Blocking the IL-4/IL-13 Axis versus the JAK/STAT Pathway in Atopic Dermatitis: How Can We Choose?

Atopic dermatitis (AD) is an immune-mediated skin disorder with a chronic-relapsing course and a multifactorial pathogenesis. In contrast to the traditional concept of AD as solely a type 2 immune-activated disease, new findings highlight the disease as highly heterogeneous, as it can be classified into variable phenotypes based on clinical/epidemiological or molecular parameters. For many years, the only therapeutic option for moderate-severe AD was traditional immunosuppressive drugs. Recently, the area of systemic therapy of AD has significantly flourished, and many new substances are now marketed, licensed, or in the last step of clinical development. Biological agents and small molecules have enriched the therapeutic armamentarium of moderate-to-severe AD, such as dupilumab, tralokinumab, lebrikizumab (monoclonal antibodies targeting the IL-4/13 pathway), abrocitinib, upadacitinib, and baricitinib (JAK inhibitors). Indeed, the AD treatment paradigm is now split into two main approaches: targeting the IL-4/13 axis or the JAK/STAT pathway. Both approaches are valid and have strong evidence of preclinical and clinical efficacy. Therefore, the choice between the two can often be difficult and represents a major challenge for dermatologists. Indeed, several important factors must be taken into account, such as the heterogeneity of AD and its classification in phenotypes, patients' comorbidities, age, and personal preferences. The aim of our review is to provide an overview of the clinical and molecular heterogeneities of AD and to explore the factors and parameters that, in clinical practice, may help inform clinical decision-making.

Neonatal protein kinase C zeta expression determines the neonatal T-Cell cytokine phenotype and predicts the development and severity of infant allergic disease

BACKGROUND

Previous studies have demonstrated that reduced T-cell protein kinase C zeta (PKCζ) expression is associated with allergy development in infants born to atopic mothers. This study examined whether this relationship extends to a general population and addressed the basis for the association.

METHODS

A flow cytometry assay was developed for the measurement of T-cell PKCζ levels in PBMC, cord blood mononuclear cell and whole blood. Cord blood T-cell PKCζ levels were measured in 135 neonates, and allergic disease was evaluated by skin prick test and clinical examination at 12 months of age.

RESULTS

Allergic children (particularly those with eczema) had significantly lower neonatal T-cell PKCζ expression than nonallergic children (P < 0.001). PKCζ levels predicted allergic disease with optimal specificity of 86% and sensitivity of 54%. The sensitivity was increased in the children of allergic mothers, who had significantly lower PKC levels than the children of nonallergic mothers. Cord blood PKCζ levels did not affect T-cell maturation in culture as assessed by CD45RA/RO expression, but low PKCζ expression was associated with reduced capacity for IFNγ production by matured T cells. Low cord blood PKC expression was further associated with increased IL-13 responses at 6 months.

CONCLUSIONS

The findings suggest a potential role for the use of PKCζ levels in cord blood T cells as a presymptomatic test to predict allergy risk in children, particularly offspring of allergic mothers, and that the basis of this relationship is related to cytokine patterns in mature T cells.

Increased IL-5 and IL-13 cytokine level in ex vivo stimulated whole blood cells from grass pollen allergic donors correlate with seasonal exposure

There is a need for simple and physiological assays to characterize the immune status of allergic individuals. Whole blood samples from 15 adult subjects (10 with positive clinical history to grass pollen and 5 with negative clinical history) were obtained before the start (April 2010) and during the middle of the grass pollen season (June 2010). The investigators were blinded to the allergic status of the subjects. A skin prick test (SPT) to grass pollen was carried out at the end of the study. Cytokines (IL-5, IL-13, IL-10 and IFNγ) and activation of T-lymphocytes were determined after ex vivo culture of whole blood cells. IL-5, IL-10 and IL-13 cytokines were significantly elevated in allergic individuals during the middle of the season (p≤0.02) compared to the start. This assay can be a valuable tool in clinical trials especially in pediatric population where limited quantities of blood are available to study immune responses.

The ocular manifestations of atopic dermatitis and rosacea

Atopic dermatitis and rosacea are chronic diseases that have both dermatologic and ocular manifestations. The occurrence of ocular disease is often proportionately higher than that of dermatologic disease. Even if the skin abnormalities appear well controlled, these patients require ophthalmic evaluation as well. Optimal management usually requires a team approach that includes internists, dermatologists, and ophthalmologists. Both disorders are characterized by acute exacerbations and require maintenance therapy for control. Exacerbations need aggressive treatment to limit ocular signs and symptoms and to reduce ocular inflammation that can lead to permanent visual loss. Topical corticosteroid use, although at times needed, should be minimized for both disorders. Future research will continue to emphasize the use of steroid-sparing and immune-modulating agents that have the potential to provide long-lasting anti-inflammatory control with a more favorable side-effect profile.

Effect of probiotics on vaccine antibody responses in infancy--a randomized placebo-controlled double-blind trial

Probiotics are immunomodulatory and may thus affect vaccine antibody responses. With the accumulating evidence of their health-promoting effects, probiotics are increasingly administered in allergy-prone infants. Therefore, we studied the effect of probiotics on antibody responses to diphtheria, tetanus and Haemophilus influenzae type b (Hib) vaccines in 6-month-old infants participating in a randomized placebo-controlled double-blind allergy-prevention trial. Mothers of unborn children at increased risk for atopy used a combination of four probiotic strains, or a placebo, for 4 wk before delivery. During 6 months from birth, their infants received the same probiotics and galacto-oligosaccharides, or a placebo. The infants were immunized with a DTwP (diphtheria, tetanus and whole cell pertussis) at ages 3, 4, and 5 months, and with a Hib polysaccharide conjugate at 4 months. Serum diphtheria, tetanus, and Hib IgG antibodies were measured at 6 months. In the probiotic group, protective Hib antibody concentrations (>/=1 microg/ml) occurred more frequently, 16 of 32 (50%) vs. six of 29 (21%) (p = 0.020), and the geometric mean (inter-quartile range) Hib IgG concentration tended to be higher 0.75 (0.15-2.71) microg/ml than in the placebo group 0.40 (0.15-0.92) microg/ml (p = 0.064). In these respective groups, diphtheria, 0.38 (0.14-0.78) vs. 0.47 (0.19-1.40) IU/ml (p = 0.449), and tetanus, 1.01(0.47-1.49) vs. 0.81 (0.56-1.39) IU/ml (p = 0.310), IgG titers were comparable. In conclusion, in allergy-prone infants probiotics seem not to impair antibody responses to diphtheria, tetanus, or Hib, but may improve response to Hib immunization.

Change in IFN-gamma-producing capacity in early life and exposure to environmental microbes

BACKGROUND

Exposure to environmental microbes in early life might lead to type 1-skewed T cell responses and therefore reduce the risk of allergic diseases.

OBJECTIVE

To investigate whether the cytokine responses at birth and at age 3 months are associated with environmental factors, especially exposure to microbes. Living in a farm, level of house dust endotoxin, cleanliness of the home, and presence of cats and dogs in the household were studied as possible determinants of cytokine production.

METHODS

Twelve farmers' and 17 nonfarmers' children were studied. Production of IL-4, IL-6, TNF-alpha, and IFN-gamma in cord blood and in peripheral blood at 3 months was measured after 8-hour and 24-hour stimulation with phorbol ester plus concanavalin A.

RESULTS

IFN-gamma responses at age 3 months were associated with farming (median, 53 vs 17 pg/mL; P = .019) and cats and dogs (49 vs 14 pg/mL; P = .014) (8 hours). Change in IFN-gamma-producing capacity from birth to 3 months was larger in children with higher than median endotoxin concentration in bed dust (P = .038) and in children with a cat or dog (P = .005) (8 hours). Increased IL-6 responses at birth were associated with cat or dog exposure (P = .004; 8 hours) and endotoxin level in settled dust (P = .039; 24 hours).

CONCLUSION

The development of IFN-gamma-producing capacity during the first 3 months of life is associated with farming, endotoxin in house dust, and cat and dog exposure. These environmental characteristics may indicate some microbial exposure capable of driving developing immune system toward T(H)1 responses.

T-cell signal transduction in children with cow's milk allergy -- increased MAP kinase activation in patients with acute symptoms of cow's milk allergy

The precise immune mechanisms behind cow's milk allergy (CMA) are still unknown. Previously, the production of the cytokines TNF-alpha and IFN-gamma in T cells from children with CMA has been shown to be decreased, and the production of IL-4 has been shown to be increased when compared to healthy children. As these aberrations in cytokine production may be associated with disturbances in cellular function, we investigated whether T-cell signal transduction is abnormal in children with CMA. For this purpose we evaluated the activation of the MAP kinase Erk2. Thirty-nine infants were included in the study. Of those with CMA, 13 had acute symptoms and 9 were free of symptoms due to a successful elimination diet at the time of the study. To activate T cells and to stimulate MAP kinase phosphorylation, peripheral blood mononuclear cells (PBMC) were incubated with Concanavalin A (ConA). The change in MAP kinase phosphorylation was measured by Western blotting. The increase in MAP kinase phosphorylation after stimulation with ConA for 5 min was significantly higher in cells from patients with acute symptoms of CMA than in cells from CMA patients free of symptoms or cells from healthy children. A time-course experiment showed that the change in MAP kinase phosphorylation was still increasing after 10 min incubation in cells from patients with acute symptoms of CMA. The increased MAP kinase activation was found to correlate positively with non-IgE mediated CMA in patients with acute symptoms of CMA.

Cytokine profiles of peripheral blood mononuclear cells from dogs experimentally sensitized to Japanese cedar pollen

Japanese cedar (Cryptomeria japonica, CJ) pollinosis is mediated by type-I hypersensitivity and induces seasonal rhinitis and conjunctivitis in humans. Previous studies showed that dogs could be experimentally sensitized with CJ pollen. In this study, we carried out quantitative analysis of mRNA levels of various cytokines in the peripheral blood mononuclear cells (PBMC) of 12 dogs experimentally sensitized to Japanese cedar pollen. Experimental sensitization was carried out by injection of crude CJ pollen extract with aluminium hydroxide gel. The expression levels of interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-18, interferon (IFN)-gamma, transforming growth factor (TGF)-beta(1), and tumor necrosis factor (TNF)-alpha mRNAs in the PBMC were quantified using a real-time sequence detection system. In the PBMC tested without culture, the expression levels of IL-8 and TNF-alpha mRNAs in experimentally sensitized dogs were significantly higher than those in control dogs. The expression level of IFN-gamma mRNA in the sensitized group was significantly lower than that in the control group. When the PBMCs were cultured in the presence of CJ pollen extract, the level of IL-4 mRNA expression was markedly increased in the PBMC from the experimentally sensitized dogs. In the PBMC stimulated with the CJ pollen extract, the expression level of IL-2 mRNA in the sensitized group was also significantly higher than that in the control group. Our data indicated that a Th2 response and proliferation of PBMC occur in response to the sensitizing antigen in dogs experimentally sensitized with CJ pollen, and revealed the presence of antigen-specific Th2 cells in this canine model. In addition, the expression levels of the mRNAs encoding proinflammatory cytokines were shown to be elevated after CJ pollen sensitization, indicating the activation of monocytes and macrophages.

T cell cytokine profiles in childhood asthma

BACKGROUND

An imbalance of T cell subsets in asthma with a predominance of Th2 type cells has been proposed. The aim of this study was simultaneously to detect surface markers and intracellular production of cytokines in T cells from the airways of children with and without asthma.

METHODS

Bronchoalveolar lavage (BAL) fluid was obtained by wedging a suction catheter into the distal airway immediately before elective surgery. Cells were stimulated with phorbol 12-myristrate 13-acetate (PMA) and ionomycin and intracytoplasmic cytokine retention was achieved using monensin. The cells were stained with the relevant antibodies and analysed by flow cytometry.

RESULTS

No statistical difference was observed between children with atopic asthma, atopic non-asthmatic subjects, and normal controls in the percentage of CD3+ cells producing interleukin (IL)-2 or IL-4. Interferon (IFN)gamma+ T cells were, however, present in a much higher percentage than either IL-2 or IL-4 positive cells. The percentage of IFNgamma+ T cells was significantly increased in subjects with atopic asthma (median 71.3%, interquartile range (IQR) 65.1-82.2, n=13) compared with both atopic non-asthmatic subjects (51.9%, IQR 37.2-70.3, n=12), p<0.05 and normal controls (58.1%, IQR 36.1-66.1, n=23), p<0.01.

CONCLUSIONS

These findings indicate that IFNgamma producing T cells are more abundant in the airways of children with atopic asthma than in atopic non-asthmatic subjects and controls. The proinflammatory activities of IFNgamma may play an important role in the pathogenesis of childhood asthma and may suggest that asthma is not simply a Th2 driven response.

Low frequency of CD4+, but not CD8+, T cells expressing interferon-gamma is related to cow's milk allergy in infancy

Low interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) production in peripheral blood mononuclear cells (PBMC) from patients with atopic dermatitis and food allergy have been reported previously. However, it remains unclear whether the weak cytokine production is caused by the imbalance of specific T-cell subsets or by dysregulation of T-cell function. In the present study we investigated the intracellular expression of these cytokines at a single-cell level to clarify the background of the disruption. Twelve of 27 breast-fed infants (0.1-8.8 months of age) had challenge-proven cow's milk allergy (CMA), and 15 infants were studied as a healthy control group. PBMC were stimulated with phorbol 12-myristate 13-acetate (PMA) and ionomycin. The frequencies of the cells expressing intracellular IL-4, IFN-gamma, and TNF-alpha were assessed using flow cytometry. In addition, at this time-point leucocyte subsets from the milk of mothers of these infants were evaluated using light microscopy. A lower number of CD8+ T cells and the defective capability of CD4+ T cells to express IFN-gamma in infant's peripheral blood co-existed with a lower number of macrophages in their mother's milk.

Expression of T helper 1 and T helper 2 cytokine mRNAs in freshly isolated peripheral blood mononuclear cells from dogs with atopic dermatitis

Using reverse transcription-polymerase chain reaction (RT-PCR) and semi-quantitative PCR techniques, mRNA expression for canine interferon (IFN)-gamma, interleukin (IL)-4, IL-5 and IL-10 in freshly isolated peripheral blood mononuclear cells (PBMCs) was examined in dogs with or without atopic dermatitis (AD). The expression of IFN-gamma mRNA in dogs with AD was lower than that in dogs without AD (healthy control). The expression of IL-5 mRNA was higher in dogs with AD than in control dogs, but there were no significant differences in IL-4 mRNA and IL-10 mRNA expression between the groups. The number of circulating eosinophils was higher in dogs with AD than in control dogs, although eosinophilia was found in only one dog with AD. These results suggest that there is a tendency for the PBMCs of atopic dogs to express a type 2 cytokine pattern that is similar to the pattern observed in human AD patients.

Biphasic cytokine expression by T cell clones from patients with atopic dermatitis with different incubation periods and strengths of stimuli

It has been proposed that T helper (Th) 2 cells play a key role in the pathogenesis of atopic dermatitis (AD) because of clinical and experimental findings including hyper IgE, eosinophilia and Th2 type cytokine overexpression, etc. In contrast, several observations such as Th1 type cytokine detection in chronic lesions and histological features resembling allergic contact dermatitis suggest that Th1 rather than Th2 cells are important for the pathogenesis of skin lesions. In order to clarify this paradox, we investigated the function of T cell clones established from AD patients. Most T cell clones induced by house dust mite antigen and interleukin (IL)-2 from peripheral blood mononuclear cells of two AD patients exhibited CD4+/ CD8-, CD45RO+/ CD45RA-, and produced high levels of IL-4 and low levels of interferon-gamma (IFN-gamma) after phytohemagglutinin (PHA) (1 microg/ml) stimulation, suggesting a Th2 subtype. When stimulated with a high dose of concanavalin A (conA) (10 microg/ml), however, these clones produced high amounts of IFN-gamma. IL-4 production reached a peak 24 hours after conA (10 ,g/ml) stimulation, whereas IFN-gamma production was increased up to 48 hours after stimulation. The findings of T cell receptor (TCR) stimulation with immobilized anti-CD3 monoclonal antibody (mAb) showed that the suitable strength of TCR stimulation for IFN-y production was higher than for IL-4. Also, in the TCR stimulated condition, the peak of IFN-gamma production was later than that of IL-4. These results indicate that T cell clones which exhibited a Th2 profile under weak stimulation can produce IFN-y in the late phase of stimulation when strong stimuli are used. The results are consistent with the previous observation that IFN-gamma production prominently appears in the chronic and late phase lesions of AD.

Increased secretion of IL-18 in vitro by peripheral blood mononuclear cells of patients with bronchial asthma and atopic dermatitis

This study was performed to determine whether or not IL-18, formerly called IFN-gamma-inducing factor, is involved in the pathogeneses of allergic disorders. Peripheral blood mononuclear cells (PBMC) were obtained from patients with allergic bronchial asthma (BA), patients with atopic dermatitis (AD) and controls who did not have any allergic disease, and then cultured with lipopolysaccharide (LPS) or phytohaemagglutinin (PHA). The concentrations of IL-18, IFN-gamma and IL-13 in supernatant fluids were determined by enzymatic immunoassaying, and the expression of IFN-gamma messenger (m) RNA in the cells was measured by colorimetric microplate assaying. IL-18 secretion in the BA patients (geometric mean (gm) = 189 pg/ml) and AD patients (gm = 172 pg/ml) was significantly higher than that in non-allergic controls (gm = 118 pg/ml). In contrast, IFN-gamma secretion in the BA patients (gm = 7.3 IU/ml) and AD patients (gm = 6.8 IU/ml) was significantly lower than that in non-allergic controls (gm = 20.7 IU/ml). The amounts of IL-13 in supernatant fluids and IFN-gamma mRNA in cells were not statistically different among the BA patients, AD patients and non-allergic controls. The possible involvement of IL-18 in allergic disorders is discussed.

Age-related changes in cytokine production by leukocytes in rhesus monkeys

Using a variety of experimental rodent and human models, age-related alterations in cytokine production by immune cells have been described extensively. While the precise mechanism(s) responsible for such age-related changes in cytokine responses remain unclear, it seems likely that these changes may have a significant effect on immune cell function. In an attempt to clarify such changes in aging primates, we examined cytokine production by white cells derived from a controlled colony of rhesus monkeys (Macaca mulatta). Non-fractionated whole blood and peripheral blood mononuclear cells (PBMCs) were obtained from male monkeys of different ages (6-28 years), and were subsequently evaluated for their ability to express mRNA and protein for the cytokines, IL-10, IL-6, IFNgamma, IL-1beta, and TNFalpha, following in vitro stimulation with polyclonal mitogens. Our results suggest that white blood cells derived from aged rhesus monkeys exhibit a significant increase in their ability to produce the Th2-associated cytokine, IL-10, upon stimulation with lipopolysaccharide (LPS) when compared to white cells derived from younger counterparts. Similarly, a significant age-related decrease in the expression of the Th1-associated cytokine, IFNgamma, was also observed using phytohemagglutinin (PHA)-stimulated PBMCs. No significant age-related differences in the production of IL-1beta or TNFalpha were observed in response to any stimulation, but there was limited evidence of an age-related increase in IL-6 production. Overall, our results suggest that a possible systemic change from a Th0/Th1 to a Th2-like cytokine profile occurs in circulating leukocytes derived from aging primates. We believe that such age-related alterations in cytokine production may play a role in the reduced immune responses observed in elderly human populations.

A high incidence of Staphylococcus aureus colonization in the external eyes of patients with atopic dermatitis

OBJECTIVE

To determine the frequency distribution of bacteria on the external surface of eyes of patients with atopic dermatitis (AD) and to investigate the relationship between the frequency of bacterial colonization and the grade of atopy or ocular diseases associated with AD.

DESIGN

Comparative cross-sectional study.

PARTICIPANTS

Thirty-six AD patients (mean age, 24.5 years) and 16 nonatopic, age-matched control participants (mean age, 25.5 years).

INTERVENTION

The eyelid margins and conjunctival sacs were scraped with sterile swabs. These samples were inoculated into aerobic and anaerobic culture media.

MAIN OUTCOME MEASURES

The frequency distribution of bacteria isolated from the eyelid margins and conjunctival sacs.

RESULTS

Bacteria isolated from AD patients were: Staphylococcus aureus in 21 of 36 patients (including methicillin-resistant Staphylococcus aureus in two patients); Staphylococcus epidermidis in two patients (including methicillin-resistant Staphylococcus epidermidis in one patient); other coagulase-negative Staphylococcus in six patients;alpha-streptococcus in three patients; Corynebacterium species in three patients; Neisseria species in two patients; and Propionibacterium acnes in one patient. From the nonatopic control participants, we isolated S. aureus in one patient, S. epidermidis in two patients and alpha-streptococcus in one patient. S. aureus was isolated from 67% of the AD patients, and any type of bacteria was isolated from 86% of the patients. These rates were significantly higher than those of nonatopic control participants (6% S. aureus and 25% any bacteria). There was no significant relationship between the frequency distribution of bacteria and the grade of atopy or associated ocular diseases.

CONCLUSIONS

High rates of bacterial colonization, especially S. aureus, were found in the conjunctival sacs and eyelid margins of AD patients. In case management of AD patients, this unique distribution of bacteria must be carefully considered.

CRTH2 is the most reliable marker for the detection of circulating human type 2 Th and type 2 T cytotoxic cells in health and disease

Cells expressing the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) and the chemokine C receptor (CCR)4 were consistently detected in the circulation of healthy subjects, whereas numbers of cells expressing CCR3 were much lower. While all CCR4+ cells were T cells, a small proportion of CRTH2+, and about a half of the few CCR3+ cells were basophils. Only CRTH2+ T cells contained Th2 or Tc2 cells, but neither Th0 or Tc0, nor Th1 or Tc1 cells, although not all of them produced Th2-type cytokines. By contrast, CCR4+ T cells contained both Th2 or Tc2 and Th0 or Tc0 cells and even Th1 or Tc1 cells, whereas the few CCR3+ T cells were not clearly classifiable for their cytokine profile. CRTH2+ T lymphocytes were virtually devoid of chemokine CX receptor (CXCR)3+ and CCR5+ cells, but enriched in CCR3+ and CCR4+ cells. By contrast, CCR3+ or CCR4+ T cells did not show a similar clear-cut dichotomy in the expression of CCR5/CXCR3 or CCR3/ CCR4. Subjects with atopic dermatitis or HIV infection with low levels of circulating CD4+ T cells revealed a significant increase of CRTH2+ cells within both the CD4+ and the CD8+ T cell subset. These data support the concept that at present CRTH2 is the more reliable marker for detection of both human Th2 and Tc2 cells in health and disease.

Atopic eczema is associated with delayed maturation of the antibody response to pneumococcal vaccine

The aim of this study was to investigate a previously undocumented observation, that children with atopic eczema under 9 years of age tended to have a poor antibody response to Pneumococcal vaccination. Thirty-five children (mean age 8.8 years, range 3-16 years) with moderate to severe atopic eczema but no history of systemic infection were studied retrospectively. Pneumococcal antibody responses after immunization with Pneumovax II were compared with a hospital control group consisting of 36 children (mean age 6.0 years, range 3-16 years) with recurrent upper respiratory tract infections. Only 17% of children with atopic eczema aged 3-8 years responded to Pneumovax. This response was significantly poorer than that of the controls (57%) (odds ratio 0.20, 95% confidence interval (CI) 0.05-0.84, P = 0.03). There were no significant differences in the levels of total IgG2, the component of IgG associated with protective antibody responses to Pneumococcus between the two groups. Delay in maturation of the total IgG and IgG2 antibody response to Pneumococcus is a feature in this group of children with moderately severe atopic eczema.

Effects of substance P and vasoactive intestinal peptide on interferon-gamma and interleukin-4 production in severe atopic dermatitis

BACKGROUND

Recent studies have demonstrated that two T cell-derived lymphokines, interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), play a crucial role in the pathogenesis of atopic dermatitis (AD). It is known that neuropeptides, such as substance P (SP) and vasoactive intestinal peptide (VIP), have various immunomodulatory effects. Elevated levels of these neuropeptides and increased staining of SP positive nerve fibers have been reported in AD patients.

OBJECTIVE

The study was designed to examine the effects of SP and VIP on the production of IFN-gamma and IL-4. The aim of the study was to establish whether these neuropeptides acted to affect cytokine release in the peripheral blood mononuclear cells (PBMCs) of AD patients.

METHODS

The effects of SP and VIP on the production of IFN-gamma and IL-4 in phytohemagglutinin stimulated PBMC cultures over a 48-hour period were analyzed by enzyme-linked immunosorbent assay in 15 AD patients. Non-atopic individuals were used as a control group.

RESULTS

Base cytokine profiles of AD patients showed significantly decreased IFN-gamma and increased IL-4 when weighed against non-atopic controls. Compared with controls, SP had a significant percentage enhancing effect on both IFN-gamma and IL-4 production at concentrations of 10(-8) M and 10(-6) M, however, this IFN-gamma up-regulatory effect of SP was reversed by spantide, a SP antagonist. The ratios of IFN-gamma: IL-4 production were significantly elevated in the SP treated AD group. Although VIP had no specific noticeable effects on the IFN-gamma and IL-4 production.

CONCLUSIONS

Our data may suggest that SP has an influence on the immunomodulation of AD patient by regulating IFN-gamma production, either directly or indirectly. Vasoactive intestinal peptide, on the other hand, has no modulatory effects on the cytokine production of AD patients.

Effects of two novel cationic staphylococcal proteins (NP-tase and p70)and enterotoxin B on IgE synthesis and interleukin-4 and interferon-gamma production in patients with atopic dermatitis

We have characterized the cell-mediated and humoral immune response of patients with atopic dermatitis (AD) and healthy controls in response to two novel staphylococcal antigens (NP-tase, p70) and the superantigen staphylococcal enterotoxin B (SEB). The parameters studied were IgE, interleukin (IL)-4 and interferon (IFN)-gamma synthesis by peripheral blood mononuclear cells (PBMC) after stimulation with NP-tase, p70 and SEB in vitro. Both antigens, as well as SEB, induced IL-4 and IFN-gamma secretion in patients and controls. However, patients with AD showed a significantly diminished IFN-gamma production in response to NP-tase or SEB. Furthermore, we demonstrated a good correlation between antigen-stimulated IgE production and the IL-4/IFN-gamma ratio in vitro. A distinct subgroup of PBMC showed impaired IFN-gamma synthesis and enhanced IL-4 secretion after incubation with p70 or NP-tase. These data support evidence that a subgroup of patients with AD, synthesizing low levels of IFN-gamma after stimulation with staphylococcal antigens, may have impaired abilities to clear Staphylococcus aureus colonization. Persistent staphylococcal antigens could then be responsible for inflammatory and allergic skin reactions in patients with AD. We therefore conclude that, besides superantigens, staphylococcal antigens may also play a part in the pathogenesis of AD.

Toward a canine model of atopic dermatitis: amplification of cytokine-gene transcripts in the skin of atopic dogs

The objectives of the present study were to characterize and compare the repertoire of cytokine-genes transcribed in skin homogenates obtained from normal dogs and dogs with atopic dermatitis (AD) using a reverse-transcriptase polymerase chain reaction and canine-specific cytokine-gene primers. Whereas IL-4 and IL-5 cytokine-gene transcripts were detected more commonly in atopic skin biopsy homogenates, IL-2 mRNA was amplified more often from normal control specimens. IFN-gamma mRNA was detected in 5/29 atopic specimens, 4 of them obtained from the only dog with chronic skin lesions. One-fourth of atopic samples exhibited clear type-2 cytokine profiles; the remainder did not demonstrate polarized repertoires. Conversely, type-1 cytokine profiles were characterized in one-fourth of normal control specimens. The present study establishes, for the first time, the transcription of type-2 cytokine-genes in the skin of dogs with AD. Future experiments investigating the cellular origin and dynamics of allergic cytokine-gene transcription are needed to confirm whether or not canine AD could be considered an immunological model for a human disease.

Cytokine-producing cells in peripheral blood of children with coeliac disease secrete cytokines with a type 1 profile

Coeliac disease (CoD) is a small intestinal disorder characterized by crypt cell hyperplasia and villous atrophy, and the production of cytokines from T cells and macrophages are of importance for the histological changes seen in CoD. A peroral immunization with an antigen, which gives rise to a mucosal immune response, may increase the levels of circulating cytokine-producing cells, and we wanted to obtain a better picture of an eventual emergence of activated circulating T cells in the peripheral blood in children with CoD. The cytokine expression of interferon-gamma (IFN-gamma), IL-4, IL-6 and IL-10 was measured at the single-cell level by an ELISPOT method in 38 children with CoD. The numbers of IFN-gamma-producing cells in the peripheral blood was increased in children with untreated CoD (P < 0.01) and after gluten challenge (P < 0.05) compared with healthy controls. Also, the numbers of IL-6-producing cells were increased (P < 0.05) after gluten challenge compared with the healthy controls. A paired comparison showed that the numbers of IFN-gamma-producing cells increased after gluten challenge (P < 0.05), whereas no such change was seen for IL-4- or IL-10-producing cells. There were no differences in the numbers of IFN-gamma-producing cells between the group of children with treated CoD and the groups of untreated or challenged CoD children. IL-4 production correlated with serum levels of total IgE. These results show that circulating mononuclear cells in children with active CoD secrete cytokines compatible with a type 1 response.

Immunoreactive interleukin 4 and interferon-gamma expression by type II alveolar epithelial cells in interstitial lung disease

Cryptogenic fibrosing alveolitis (CFA), extrinsic allergic alveolitis (EAA), and sarcoid are all immunologically mediated forms of interstitial lung disease. In contrast to most patients with EAA and sarcoid, patients with CFA show relentless pulmonary fibrosis which is unresponsive to immunosuppressive therapy. Previous studies have indicated a possible role for epithelial-derived cytokines in the regulation of immunological and fibrotic responses in the lung. This study has examined lung biopsy specimens from patients with CFA, EAA, and sarcoid for immunoreactive interleukin 4 (IL4) and interferon-gamma (INFgamma) expression by type II alveolar epithelial cells, as these cytokines have been suggested to have in vitro stimulatory and inhibitory effects on fibroblast function. In addition, mRNA in situ hybridization was performed on the CFA lung biopsies to confirm transcription of these cytokine genes within the cells. The results show that type II epithelial cells in EAA and sarcoid show up-regulation of immunoreactivity for both IL4 and INF-gamma, but that in CFA only IL4 is detectable. The mRNA in situ hybridization results indicate that this may represent post-transcriptional regulation of INFgamma expression in CFA. These results are consistent with previous observations of a paucity of INFgamma and a predominantly type II (Th2-like) pattern of immune response in patients with CFA and suggest a possible imbalance of pro-fibrogenic cytokines in the distal lung of patients with this condition, compared with those with EAA or sarcoid.

Intracellular interferon-gamma (IFN-gamma) production in normal children and children with atopic dermatitis

A reduction in the in vitro production of IFN-gamma has been consistently described in atopic dermatitis (AD). Whether this reduction is due to a decrease in the population of peripheral blood mononuclear cells (PBMC) producing IFN-gamma or reduced IFN-gamma production per cell, or a combination of both is not clear. We have examined the intracellular production of IFN-gamma in children with AD and in healthy non-atopic controls. As Staphylococcus aureus colonization is a feature of childhood AD, and is postulated to contribute to the cutaneous inflammation in atopic dermatitis, S. aureus and Staphylococcal enterotoxin B (SEB) were used to activate PBMC. Stimulated PBMC from subjects with AD had significantly fewer IFN-gamma-containing cells in response to SEB (P < 0.001) and S. aureus (P < 0.01) than normal non-atopic children. In addition, SEB-stimulated PBMC from children with AD had less IFN-gamma per cell than normal non-atopic children (P < 0.01). Reduction in the proportion of cells containing IFN-gamma was seen in CD4+, CD8+ and natural killer (NK) cells in PBMC from children with AD. Our findings indicate that reduced production of IFN-gamma observed in childhood AD is due to both a decrease in the number of IFN-gamma-producing cells and a reduced amount of IFN-gamma production per cell. Furthermore, we found that this defect was not confined to CD4+ T cells, suggesting a more generalized defect in IFN-gamma production in childhood AD.

Serum IgE level is negatively correlated with the ability of peripheral mononuclear cells to produce interferon gamma (IFNgamma): evidence of reduced expression of IFNgamma mRNA in atopic patients

BACKGROUND

In patients with atopic diseases such as bronchial asthma and atopic dermatitis, an elevated serum IgE level is common. Several studies showed that interleukin-4(IL-4) and interferon-gamma (IFNgamma) are important for regulation of IgE production.

OBJECTIVES

The study was designed to examine the pathogenesis of an elevated serum IgE level at the production levels of TH1-type and TH2-type cytokines.

METHODS

The production of interleukin-2 (IL-2), IL-4, interleukin-5 (IL-5) and IFNgamma by peripheral blood mononuclear cells (PBMCs) stimulated with phytohemagglutinin (PHA) was analysed in 20 individuals with various serum IgE levels. The amount of IFNgamma mRNA in the stimulated PBMCs was analysed using a quantitative polymerase chain reaction method.

RESULTS

Cytokine production was analysed simply as a function of serum IgE level. The serum IgE level was negatively correlated with the amount of IFNgamma secreted by PBMCs (n = 20, R = -0.724, P<0.005) when logarithmically transformed data were analysed, but were not or were only weakly correlated with those of IL-4, IL-2, or IL-5 secreted by these cells (n = 20). For investigation of the cause of reduced IFNgamma production in individuals whose serum IgE level are high, the amount of IFNgamma mRNA was determined. The levels of IFNgamma mRNA expression in the stimulated PBMCs correlated well with the amount of IFNgamma secreted by the PBMCs (n = 8, R = 0.947, P < 0.001).

CONCLUSIONS

Reduced IFNgamma production ability due to reduced IFNgamma mRNA expression in PBMCs is associated with an elevated serum IgE level in atopic patients.

Reduced interferon-gamma but normal IL-4 and IL-5 release by peripheral blood mononuclear cells from Xhosa children with atopic asthma

BACKGROUND

Allergic asthma is increasing in black South Africans, a cohort with inherently high basal IgE levels. Atopy has been linked to an excess of the T helper 2 cytokines IL-4 and IL-5 relative to the T helper 1 cytokine interferon-gamma (IFN-gamma); however, most studies have utilized T cell clones. Studies on peripheral blood mononuclear cells (PBMC) have shown decreased IFN-gamma release in patients with atopic dermatitis. It is uncertain whether this finding extends to atopic asthma.

OBJECTIVES

To characterize cytokine release by mitogen-activated PBMC from Xhosa children and to investigate whether reduced IFN-gamma release is a feature of atopic asthma and whether there is a relationship between cytokine profiles and asthma severity.

METHODS

Cytokine release and proliferation of phytohemagglutinin-stimulated PBMC from 10 patients with severe asthma and 14 patients with moderate asthma (highly allergic to house dust mites) and 17 healthy controls was assessed. Total serum, allergen-specific, and Ascaris-specific IgE was measured.

RESULTS

Proliferation did not differ between the groups. The release of IFN-gamma was progressively decreased (and the IL-4/IFN-gamma ratio increased) in the groups with moderate or severe asthma. Tumor necrosis factor-alpha release was reduced, but IL-4, IL-5, and granulocyte-macrophage-colony stimulating factor release was unchanged. The presence of Ascaris-specific IgE did not influence the cytokine profiles.

CONCLUSION

Our study extends the findings observed for other atopic disorders and suggests that defective IFN-gamma release is a generalized feature of atopic diseases. This study-the first to investigate both severe and moderate asthma, with the groups having similar atopic profiles-indicates that the extent of the defect in IFN-gamma release might be related to asthma severity.

Immunocytochemical and flow cytofluorimetric detection of intracellular IL-4, IL-5 and IFN-gamma: applications using blood- and airway-derived cells

We have compared an immunocytochemical and a flow cytofluorimetric method to detect intracellular IFN-gamma, IL-4 and IL-5 in T-cell clones, peripheral blood mononuclear cells (PBMC) and bronchoalveolar lavage fluid (BALF) cells. Intracellular bound cytokine-specific antibodies were visualized either with amino-ethyl carbazole (for immunocytochemistry), or with fluorescent antibodies (for flow cytofluorimetry). The staining was inhibited with recombinant cytokines and corresponded qualitatively and quantitatively to cytokine levels in the supernatants of T-helper-0 (Th0), Th1 and Th2 clones. In analysing in vitro stimulated cells, sufficient signal in the fluorimetric assay was only obtained after the addition of monensin to the cultures. We then observed a good correlation between immunocytochemical (with no monensin added) and the flow cytofluorimetric staining for all three cytokines (PBMC, IFN-gamma and IL-4, rho = 0.9, no IL-5 detectable; clones, IL-5, rho = 0.81, all three p < 0.05). However, compared to flow cytometry, a greater percentage of positively stained cells was frequently observed using immunocytochemistry. In BALF cells, the immunocytochemical method was able to detect significant percentages of positive cells without in vitro stimulation of the cells, in contrast to the flow cytofluorimetric method. In BALF cells from sarcoidosis patients, T-cells were mainly IFN-gamma-positive (immunocytochemically assessed), both with (mean +/- SEM, 39.7 +/- 9.8%), and without (3.5 +/- 1.3%) in vitro stimulation. In BALF cells from allergic subjects, the immunocytochemical method showed lymphocytes positive for IFN-gamma (40.3 +/- 8.3%), IL-4 (19.1 +/- 0.49) and IL-5 (6.1 +/- 3.1). We conclude that both methods can be used to assess the production of IFN-gamma, IL-4 or IL-5 at the single-cell level in T-cell clones, PBMC and cells from the BALF. The high sensitivity and the low number of cells required for the immunocytochemical method indicate that this method can provide detailed information on cytokine production of airway-derived cells in diseases with airway inflammation such as sarcoidosis and asthma.

Development of immune functions related to allergic mechanisms in young children

The newborn immune system differs quantitatively and functionally from that of adults. Development of the immune system has important implications for childhood diseases. The immaturity of the immune system in the first years of life may contribute to failure of tolerance induction and in the development of allergic disease. T cell function is diminished, especially the capacity to produce cytokines; production of interferon (IFN)-gamma, and IL-4 is strongly reduced. IFN-gamma has been found to be even lower in cord blood of newborns with a family history of atopy. Differences in other cell types (natural killer cells, antigen-presenting cells, and B cells) could also play a role in the development of allergic disease. Current data suggest that irregularities in IgE synthesis, helper T cell subsets (Th1, Th2, CD45RA, and CD45RO), cytokines (IL-4, IFN-gamma), and possibly other cell types may play a role in the development of allergy in childhood. Moreover, the role of cell surface molecules, like co-stimulatory molecules (CD28, CD40L), activation markers (CD25), and adhesion molecules (LFA-1/ICAM-1, VLA-4/ VCAM-1) is also discussed. These variables are modulated by genetic (relevant loci are identified on chromosome 5q, 11q, and 14) and environmental forces (allergen exposure, viral infections, and smoke). The low sensitivity of current predictive factors for the development of allergic diseases, such as cord blood IgE levels, improves in combination with family history and by measurement of in vitro responses of lymphocytes and skin reactivity to allergens. New therapeutic approaches are being considered on the basis of our current understanding of the immunopathology of allergic disease, for instance cytokine therapy and vaccination with tolerizing doses of allergen or peptides.

Kinetics and functional implications of Th1 and Th2 cytokine production following activation of peripheral blood mononuclear cells in primary culture

The importance of cytokine production in some disease processes is now widely recognized. To investigate temporal relationships between cytokines, we stimulated peripheral blood mononuclear cells (PBMC) in vitro using the T cell mitogen phytohemagglutinin (PHA) and various antigens chosen to induce predominantly Th1 (streptokinase: streptodornase or purified protein derivative) or Th2 (Dermatophagoides pteronyssinus, bee or wasp venom: allergens in sensitive subjects) responses. Cytokine production was measured by sensitive bioassays or enzyme-linked immunosorbent assays. Of the 30 subjects studied, 10 were normal and 20 individuals were allergic to either D. pteronyssinus (n = 10) or bee venom (n = 10) (examined before specific allergen immunotherapy). We examined the temporal profiles of a panel of cytokines produced in primary culture. In PHA-driven cultures, cytokines were found to be sequentially produced in the order interleukin (IL)-2, IL-4, IL-5, IL-3, interferon (IFN)-gamma, IL-10, IL-6, IL-12 and tumor necrosis factor (TNF)-alpha. The response to allergen in allergic patients was predominantly Th2 in nature, with the production of IL-4, IL-5, IL-6 and IL-10, but little or no IFN-gamma. IL-2, IL-3, TNF-alpha and IL-12 were also produced in low amounts. The response of both atopic and normal subjects to recall bacterial antigens was predominantly Th1, with high levels of IFN-gamma, IL-2 and TNF-alpha. The relevance of the order, amount and speed of production, characteristic kinetics (production, consumption, homeostatic regulation) and the cell source of the cytokines are discussed.

Expression of interferon-gamma (IFN-gamma), IL-10, IL-12 and transforming growth factor-beta (TGF-beta) mRNA in synovial fluid cells from patients in the early and late phases of rheumatoid arthritis (RA)

The expression of immunoregulatory cytokines was investigated in freshly isolated synovial fluid mononuclear cells (SFMC) and peripheral blood mononuclear cells (PBMC) from patients with RA, using a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay. IFN-gamma, TGF-beta, IL-10 and IL-12 (p40) transcripts were detected in SFMC of patients with early disease (<1 year duration) as well as in patients with long standing arthritis (>1 year). The expression of IFN-gamma, IL-10 and IL-12 mRNA was increased in SFMC compared with RA PBMC. In addition, the expression was higher in RA SFMC than in PBMC from health control individuals. Immunoassay analysis of the secreted IL-12 heterodimer demonstrated increased levels in RA SF compared with levels found in serum from RA patients and control individuals. High levels of TGF-beta mRNA were found in SFMC, but a significantly decreased TGF-beta/beta2-microglobulin (beta2-M) ratio was found compared with PBMC from both patients and control individuals. IL-4mRNA could not be detected, either in SFMC or in PBMC. Cytokine expression in RA PBMC did not differ from control PBMC, with the exception of a decreased TGF-beta/beta2-M ratio in RA patients with early disease. Our findings of IFN-gamma mRNA and IL-12, but undetectable levels of IL-4 mRNA, suggest that the synovitis is characterized by a type 1 immune response. The presence of TGF-beta and IL-10 mRNA indicates that immunosuppressive cytokines may also operate in the inflamed joint, although their level of expression may not be sufficient for down-modulation of immune activation.

Role and modulation of T-cell cytokines in allergy

Allergic sensitization and the development of effector functions are controlled by IL-4-secreting and IL-5-secreting type 2 T cells. Recent studies have provided new insights into the events triggering the development of type 1 and type 2 T cells, the discrimination of type 1 and type 2 effector T cells from various T-cell subsets, and the improvement of established and new therapeutic strategies, which are aimed at modulating such T-cell functions in the allergic patient.

The central rôle of T-cells in allergic sensitization and IgE regulation

The atopic phenotype develops on the basis of a genetic predisposition. Several candidate genes and chromosomal regions have been recently identified that may play a rôle in the development of allergic sensitization and total IgE production, including genes encoding MHC and T-cell receptor (TCR) molecules, cytokines and others. Genetic predisposition triggers and immunological dysregulation which is controlled by CD4+ T-cells. (Specialized) antigen presenting cells process and present allergenic peptides (T-cell epitopes) on MHC class II molecules to T-cells that recognize MHC plus peptide using the TCR. Cognate and non-cognate interaction results in T-cell activation. Selective stimulation of the allergen specific T-cells is the result of allergen-specific sensitization. These T-cells are characterized by (simultaneous) production of IL-3, IL-4, IL-5 (and may be IL-13). These cytokines control the production of IgE by B cells and play a critical rôle in the activation and differentiation of effector cells of the allergic response (such as eosinophils and mast cells). In addition to MHC-TCR interaction and cytokine production, ligation of CD40 and CD40L represents an additional requirement for the production of functional IgE molecules. Immediate hypersensitivity responses are characterized by an early phase response (triggered by many mediators released from effector cells following allergen exposure, IgE cross-linking and activation of signal transduction pathways) and a late phase response that is mediated to a large extend by the influx of T-cells and effector cells into the site of allergic inflammation. Deliniation of the immunological mechanisms that result in allergic sensitization will contribute to the development of specific immunomodulatory strategies aimed to prevent the development of allergies.

Interleukin-4 and interferon-gamma production in atopic and non-atopic children with asthma

Previous studies have demonstrated increased production of interleukin-4 (IL-4) and reduced production of interferon (IFN)-gamma in stimulated peripheral blood mononuclear cell cultures from children and adults with atopic dermatitis, however, it is unclear whether such an imbalance of cytokine production relates to other childhood atopic diseases such as asthma, and in particular to the presence of the atopic state per se. The production of IL-4 and IFN gamma in phytohaemagglutin- (PHA)-stimulated peripheral blood mononuclear cell (PBMC) cultures from atopic and non-atopic children with moderately severe chronic persistent asthma, and a group of age-matched non-atopic controls who did not have asthma was examined. Atopic children with asthma produced significantly more IL-4 and less IFN gamma than non-atopic children with asthma and non-atopic controls who did not have asthma. There was no significant difference in IL-4 or IFN gamma production between non-atopic children with asthma and controls. These findings demonstrate that an imbalance of IL-4 and IFN gamma production is present in atopic asthma as previously documented in atopic dermatitis, therefore suggesting that it is a feature of the atopic state per se.

Interferon-gamma in the treatment of atopic dermatitis: influence on T-cell activation

Atopic dermatitis (AD) is a chronic relapsing skin disease characterized by various immunologic abnormalities. Its pathogenesis remains obscure and its treatment difficult. We have studied the efficacy of systemic recombinant human interferon-gamma (rhIFN-gamma) treatment (0.05 mg/m2 sc on 3 consecutive days, during 4 weeks) in 10 patients with severe AD. Marked clinical improvement was observed starting from the third week of treatment. Erythema, dryness, and lichenification were the most responsive symptoms. Serum immunoglobulin E and IgG4 levels did not change during treatment. Blood eosinophil count decreased only transiently at the end of the first and second series of injections (days 4 and 11; P = 0.02). Patients with AD showed an increase in CD25-positive cells (11.0% vs 4.88%; P = 0.0001) as compared to 10 age-matched healthy controls. Moreover, in parallel with clinical improvement, a distinct decrease in CD25-positive lymphocytes was observed on days 32 and 50 (P = 0.002 and P = 0.006, respectively). We suggest that in AD the beneficial effect of rhIFN-gamma might be related to the inhibition of excessive T-cell activation, perhaps of the subpopulations, producing interleukin (IL)-4 and IL-5.

Spontaneous expression of IL-4 mRNA in lymphocytes from children with atopic dermatitis

Normal lymphocytes do not generally produce or secrete lymphokines in the resting or unstimulated state and only express or release cytokines following activation. Recently, the spontaneous production of intracellular interferon-gamma (IFN-gamma) and spontaneous secretion of IL-6 has been documented in patients with atopic dermatitis. These findings indicated that lymphocytes had been previously activated in vivo. Such in vivo activation may also be associated with spontaneous production of IL-4. As measurement of IL-4 secretion by immunoassay is complicated by poor sensitivity, and only provides information on the net amount of cytokine present after secretion, adsorption, consumption and degradation have occurred, IL-4 mRNA expression in peripheral blood lymphocytes from children with atopic dermatitis and controls was examined by polymerase chain reaction (PCR)-assisted mRNA amplification. Spontaneous expression of IL-4 mRNA was detected in four of eight patients with severe atopic dermatitis. Following stimulation in vitro, seven of eight atopic patients demonstrated detectable IL-4 mRNA. In comparison, no spontaneous expression of IL-4 mRNA was found in controls, and only six of 10 controls expressed IL-4 mRNA in stimulated cultures. The spontaneous expression of IL-4 mRNA in unstimulated cultures from children with atopic dermatitis supports the possibility that previous in vivo activation has occurred, and suggests that IL-4 production is increased in vivo in atopic dermatitis. This in vivo activation together with the constitutive expression of IL-4 mRNA are likely to contribute to the spontaneous in vitro production of IgE in atopic patients.