Atopic dermatitis: immunobiology and treatment with immune modulators

Atopic dermatitis (AD), a chronic inflammatory skin disease, is frequently seen in patients with a personal or family history of asthma and allergic rhinitis. Population studies suggest an increasing prevalence of AD in children since World War II, with 10-15% of the population being affected by AD at some time during childhood. In patients with moderate to severe AD, involvement can be life-long, causing significant interference with school, work and social interactions. The term atopic dermatitis was introduced to reflect the close association between AD and respiratory allergy. During the past decade, extraordinary progress has been made in our understanding of the immunopathogenesis of allergic diseases. In particular, this constellation of inherited illnesses has now been demonstrated to be associated with activation of a specific group of cytokine genes encompassing IL-3, IL-4, IL-5, IL-13 and granulocyte-macrophage colony-stimulating factor (GM-CSF). The molecular basis for selective activation of this cytokine gene cluster and the immunological consequences are now being pursued actively by many laboratories. However, it is clear that allergic diseases result from a polygenic inheritance pattern which involves not only cytokine gene activation but also activation of other less well defined gene products. Furthermore, the clinical expression of allergic diseases is highly dependent on a complex interaction between the host and its environment, e.g. allergen exposure. The genetic predisposition to develop allergic responses may be similar in patients with AD and other allergic diseases, such as asthma. However, targeting of the allergic immune response may relate to the organ in which allergen sensitization first occurs; the capacity of immune effector cells, e.g. T lymphocytes, to home preferentially to the skin versus the respiratory mucosa; and the programmed response of resident cells, e.g. epithelial cells, to injury and inflammation. This review examines the cellular and immunological mechanisms that are thought to play an important role in the pathogenesis of chronic AD. An understanding of the immunological basis of AD is likely to have important clinical implications in our approach to the management of this common illness, and the development of immunomodulators for its treatment.

Effects of glucocorticoids on lymphocyte activation in patients with steroid-sensitive and steroid-resistant asthma

BACKGROUND

Glucocorticoids are important medications used to control the airway inflammation associated with asthma. Synthetic glucocorticoids vary in their binding affinity for the glucocorticoid receptor (GCR).

METHODS

We compared hydrocortisone, beclomethasone dipropionate, triamcinolone acetonide, flunisolide, and budesonide with regard to their capacity to inhibit phytohemagglutinin-induced peripheral blood mononuclear cell proliferation from six patients with steroid-sensitive asthma and seven patients with steroid-resistant asthma. Peripheral blood mononuclear cell GCR binding affinities for dexamethasone and budesonide were also determined for both patient groups by using a radioligand binding assay and Scatchard analysis.

RESULTS

Dose-dependent inhibition was demonstrated for all glucocorticoids in both patient groups, with the steroid-resistant group requiring approximately 2 log-fold more glucocorticoids for an equivalent degree of inhibition. The mean concentrations necessary to cause 50% inhibition of lymphocyte proliferation (IC50s) for the steroid-sensitive group ranged from 2 x 10(-10) mol/L for budesonide to 7 x 10(-8) mol/L for hydrocortisone, whereas the mean IC50s for the steroid-resistant group ranged from approximately 2 x 10(-8) mol/L for budesonide to greater than 10(-6) mol/L for hydrocortisone. In addition, a significant correlation was noted between the degree of inhibition of lymphocyte proliferation (IC50) and the binding affinity of dexamethasone to the GCR. Patients with steroid-resistant asthma have been shown to have a reduced GCR binding affinity. The GCR binding affinity for budesonide was significantly higher in both groups (i.e., lower dissociation constant) than that obtained for dexamethasone.

CONCLUSION

These data suggest that glucocorticoids such as budesonide, by virtue of their high GCR binding affinities and greater ability to suppress lymphocyte proliferation, may therefore be beneficial in the management of difficult-to-control asthma.

Left ventricular function after valve repair for chronic mitral regurgitation: predictive value of preoperative assessment of contractile reserve by exercise echocardiography

OBJECTIVES

We evaluated the value of preoperative assessment of left ventricular contractile reserve in predicting ventricular function after valve repair for minimally symptomatic mitral regurgitation.

BACKGROUND

The optimal timing for operation in minimally symptomatic patients with significant mitral regurgitation is controversial. Accurate preoperative assessment of left ventricular function is difficult, and the ability to predict postoperative function is limited. Previous studies in patients undergoing mitral valve replacement may not be applicable in the present era of valve repair.

METHODS

We performed exercise echocardiography in 139 patients with isolated mitral regurgitation and no coronary disease, 74 of whom subsequently underwent uncomplicated valve repair. We measured rest left ventricular end-systolic dimension, end-systolic wall stress and positive first derivative of left ventricular pressure (dP/dt). End-diastolic and end-systolic volumes and ejection fraction were measured preoperatively at rest, immediately after exercise and postoperatively.

RESULTS

Ejection fraction decreased postoperatively to 55 +/- 10% from a rest preoperative value of 64 +/- 9% (p < 0.001). Compared with patients with a postoperative ejection fraction > or = (n = 56), patients with postoperative ejection fraction < 50% (n = 18) had a significantly lower preoperative exercise ejection fraction (57 +/- 11% vs. 73 +/- 9%, p < 0.0005), a larger exercise end-systolic volume index (32 +/- 8 vs. 18 +/- 7 cm3/m2, p < 0.0005) and a lower change in ejection fraction with exercise (-4 +/- 8% vs. 9 +/- 10%, p < 0.005). Preoperative rest indexes, including dP/dt, end-systolic wall stress and end-systolic volume index were less predictive, whereas exercise capacity, rest ejection fraction and end-systolic dimension were not predictive of post-repair ejection fraction. An exercise end-systolic volume index > 25 cm3/m2 was the best predictor of postoperative dysfunction, with a sensitivity and specificity of 83%.

CONCLUSIONS

In minimally symptomatic patients with mitral regurgitation, latent ventricular dysfunction may be indicated by a limited contractile reserve, manifest at exercise as an inadequate increase in ejection fraction and a larger end-systolic volume. These variables may also be used to predict left ventricular function after repair.

The potential role of gastroesophageal reflux in the pathogenesis of food-induced wheezing

Severe reactive airways disease (RAD) in children is frequently associated with gastroesophageal reflux or food allergy. However a relationship between these two confounding factors has yet to be investigated. We postulate that, in certain patients with micro-aspiration of gastric contents into the airways, food allergens sensitize T cells in the peribronchial lymphoid tissue and induce the production of food-specific IgE antibodies that sensitize airway cells. Subsequent exposure to these food allergens might then induce IgE dependent mediator release from mast cells as well as T cell and eosinophil activation, thus contributing to airway inflammation and RAD. In the current report, we describe the case of a patient with severe asthma who had food allergy and gastroesophageal reflux whose clinical findings support this hypothesis. We also provide additional evidence for a high rate of food sensitization in patients with bronchopulmonary dysplasia (BPD), RAD and GER. We conclude that additional studies are warranted to examine the possibility that patients who have RAD and GER require an evaluation for food allergy.

The role of glucocorticoids in the management of asthma

Glucocorticoids (GCs) are a highly effective class of medication used in the treatment of airway inflammation associated with chronic asthma. Nevertheless, there remain concerns regarding potential adverse effects accompanying the use of systemic and high-dose inhaled GC therapy. Recent studies also suggest that there is high variability in airway response to GCs. Indeed, the immunopathogenesis of a subset of asthmatics poorly responsive to glucocorticoid therapy have been studied and may provide new insights into mechanisms by which glucocorticoids act in chronic asthma. The current review will examine a number of these issues, particularly mechanisms by which GCs act in asthma, the immunology of steroid resistance, and adverse effects associated with GC treatment.

Steroid-resistant asthma: evaluation and management

LEARNING OBJECTIVES

Reading this article will reinforce the reader's knowledge of the definition, pathophysiology, differential diagnosis, and treatment of the steroid-resistant asthmatic patient.

DATA SOURCES

Prospective and retrospective data from the authors' experience were evaluated. In addition, a Medline database was searched from 1981, using the key words "asthma," "glucocorticoids," and "glucocorticoid resistance" with the restrictions of English language and human subjects. Relevant articles referenced in retrieved sources and current texts on severe asthma were also utilized.

STUDY SELECTION

Data source abstracts, pertinent articles, and book chapters meeting the objectives were critically reviewed.

RESULTS

Although rare, individuals with steroid-resistant asthma are often the most difficult-to-manage asthmatic patients in that they have severe disease yet fail to respond to glucocorticoids. To make the diagnosis of steroid-resistant asthma, the patient must fail to respond to a 7 to 14-day course of daily prednisone as measured by less than a 15% improvement in morning prebronchodilator FEV1 following the glucocorticoid course. Ongoing inflammation is thought to play a major role in the pathogenesis of steroid-resistant asthma, and recent studies have demonstrated diminished glucocorticoid receptor to glucocorticoid, or diminished glucocorticoid receptor to DNA binding as possible mechanisms for diminished glucocorticoid responsiveness. Alternative asthma therapies such as methotrexate, cyclosporine, and intravenous gammaglobulin are often used in this group of asthmatic patients.

CONCLUSIONS

The patient with steroid-resistant asthma presents several challenges. These individuals often display many of the sequelae of long-term systemic glucocorticoid use while achieving little therapeutic benefit. Prior to making the diagnosis of steroid-resistant asthma, diseases that can contribute to poor control of asthma must be ruled out, and noncompliance issues addressed. Alternative asthma therapies are often used; however, they also carry the potential for adverse effects, and have not been thoroughly studied in this population of asthmatic patients.

Staphylococcal toxins and protein A differentially induce cytotoxicity and release of tumor necrosis factor-alpha from human keratinocytes

It has been proposed that toxins and other bacterial protein products of Staphylococcus aureus can act as triggers or persistence factors in several inflammatory skin diseases. In this study, we examined the S. aureus isolates from the skin of patients with atopic dermatitis and psoriasis. We found that the bacterial isolates from these patients exhibited either characteristic superantigenic toxins or thermolabile toxins believed to be staphylococcal alpha-toxin. All of these staphylococcal strains also secreted extracellular staphylococcal protein A. We found significant differences in the action of these toxins on human keratinocytes and keratinocyte cell lines. The superantigenic toxins toxic shock syndrome toxin-1, staphylococcal enterotoxins A and B, and exfoliative toxin-A, as well as staphylococcal protein A, did not induce significant cytotoxic damage in the keratinocyte cell line HaCaT, whereas the staphylococcal alpha-toxin produced profound cytotoxicity. Keratinocyte cytotoxicity induced by staphylococcal alpha-toxin was time and concentration dependent and demonstrated the morphologic and functional characteristics of necrosis, not apoptosis. Addition of alpha-toxin to keratinocytes simultaneously induced cell lysis and tumor necrosis factor-alpha release into the medium within 30 min; apparently, it was constitutive tumor necrosis factor-alpha. On the other hand, superantigenic toxins and, in particular, protein A showed stimulation of tumor necrosis factor-alpha secretion in keratinocytes and release of this cytokine after 6-12 h of incubation. Thus, staphylococcal protein A, alpha-toxin, and superantigenic toxins found in S. aureus isolates from patients with psoriasis and atopic dermatitis can produce direct pro-inflammatory effects on keratinocytes through the release of tumor necrosis factor-alpha. We propose that these effects may be relevant to the induction and persistence of lesions in these two diseases.

Eosinophil infiltration in nonallergic chronic hyperplastic sinusitis with nasal polyposis (CHS/NP) is associated with endothelial VCAM-1 upregulation and expression of TNF-alpha

We studied potential mechanisms of eosinophil accumulation in nonallergic chronic hyperplastic sinusitis with nasal polyposis (CHS/NP). We measured expression of endothelial vascular cell adhesion molecule-1 (VCAM-1), which mediates selective eosinophil transendothelial migration, the cytokines interleukin (IL)-1 beta, TNF-alpha and IL-13 which upregulate VCAM-1 expression, and the chemokine RANTES which mediates lymphocyte, monocyte, and eosinophil chemotaxis in chronic hyperplastic sinusitis with nasal polyposis (CHS/NP) nasal polyps (nonallergic versus allergic) and middle turbinate biopsies from normal controls. By immunohistochemical staining, the density of EG2+ eosinophils was increased in both the nonallergic and allergic CHS/NP subgroups compared to normal controls. VCAM-1 expression was significantly increased in CHS/NP subjects compared to normal controls (P = 0.0005), with the highest intensity seen in nonallergic CHS/NP. By in situ hybridization, the densities of IL-1 beta, TNF-alpha, IL-13, and RANTES mRNA+ cells were all increased in nonallergic CHS/NP compared to normal controls (P = 0.009, 0.0005, 0.0005, and 0.001, respectively). In comparison to allergic CHS/NP, nonallergic CHS/NP had a significantly higher tissue density of TNF-alpha (P = 0.04) and a lower density of IL-13 (P = 0.005) mRNA+ cells. In general, VCAM-1 expression correlated strongly in CHS/NP with the density of TNF-alpha (R = .91, P = 0.0005) but not the density of IL-1 beta, IL-13, or RANTES mRNA+ cells. We conclude that upregulation of VCAM-1 and elaboration of RANTES may contribute to the marked accumulation of eosinophils in nonallergic CHS/NP. TNF-alpha may play a critical role in VCAM-1 upregulation in this nonallergic eosinophilic disorder.

A novel action of IL-13: induction of diminished monocyte glucocorticoid receptor-binding affinity

We have recently demonstrated that the combination of IL-2 and IL-4 blunts T cell responses to glucocorticoids in steroid resistant (SR) asthma by reducing glucocorticoid receptor (GCR)-binding affinity. Since immune activation appears to be involved in the acquisition of steroid resistance, we sought to identify whether other cytokines could also induce diminished GCR-binding affinity. In the current report, utilizing a [3H]dexamethasone radioligand-binding assay and Scatchard analysis, we found that IL-13, a cytokine with similar actions as IL-4, could induce diminished GCR binding-affinity (GCR Kd = 34.4 +/- 2.3 nM with IL-13 vs Kd = 8.8 +/- 0.7 nM for unstimulated control cells; p < 0.001) in PBMC from normal subjects. In contrast, PBMC incubated with IL-1, IL-3, IL-5, IL-7, IL-8, IL-12, or granulocyte-macrophage-CSF had no effect on GCR-binding affinity; and no additive effect to the decreased GCR-binding affinity was noted when IL-13 was cocultured with IL-2 or IL-4. The cell target of IL-13-induced GCR effects was studied and found to reside in the non-T cell population; specifically, the monocyte fraction. To determine the functional significance of the decreased GCR-binding affinity, monocytes were pretreated with and without IL-1 3 prior to stimulation with LPS and hydrocortisone. IL-13 pretreatment of monocytes significantly diminished (p = 0.005) the suppressive effects of hydrocortisone on LPS-induced IL-6 production. IL-13, by virtue of its ability to induce diminished GCR-binding affinity, may contribute to impaired GC responsiveness during inflammatory illnesses.

A novel action of IL-13: induction of diminished monocyte glucocorticoid receptor-binding affinity

We have recently demonstrated that the combination of IL-2 and IL-4 blunts T cell responses to glucocorticoids in steroid resistant (SR) asthma by reducing glucocorticoid receptor (GCR)-binding affinity. Since immune activation appears to be involved in the acquisition of steroid resistance, we sought to identify whether other cytokines could also induce diminished GCR-binding affinity. In the current report, utilizing a [3H]dexamethasone radioligand-binding assay and Scatchard analysis, we found that IL-13, a cytokine with similar actions as IL-4, could induce diminished GCR binding-affinity (GCR Kd = 34.4 +/- 2.3 nM with IL-13 vs Kd = 8.8 +/- 0.7 nM for unstimulated control cells; p &lt; 0.001) in PBMC from normal subjects. In contrast, PBMC incubated with IL-1, IL-3, IL-5, IL-7, IL-8, IL-12, or granulocyte-macrophage-CSF had no effect on GCR-binding affinity; and no additive effect to the decreased GCR-binding affinity was noted when IL-13 was cocultured with IL-2 or IL-4. The cell target of IL-13-induced GCR effects was studied and found to reside in the non-T cell population; specifically, the monocyte fraction. To determine the functional significance of the decreased GCR-binding affinity, monocytes were pretreated with and without IL-1 3 prior to stimulation with LPS and hydrocortisone. IL-13 pretreatment of monocytes significantly diminished (p = 0.005) the suppressive effects of hydrocortisone on LPS-induced IL-6 production. IL-13, by virtue of its ability to induce diminished GCR-binding affinity, may contribute to impaired GC responsiveness during inflammatory illnesses.

Triggering through CD40 promotes interleukin-4-induced CD23 production and enhanced soluble CD23 release in atopic disease

The pathogenesis of atopic disease is closely linked to the overproduction of IgE. CD23 and CD40 are two cellular receptors involved in the regulation of IgE production and both receptors are elevated in atopic disease. We have examined the role of CD40 in the regulation of CD23 and soluble CD23 production in healthy and atopic donors. Triggering of the B cell CD40 receptor directly enhances interleukin (IL)-4-mediated up-regulation of CD23 at both the protein and the mRNA level. When atopic donors were studied, the synergistic effect of CD40 triggering on the IL-4-induced up-regulation of CD23 and soluble CD23 (sCD23) was enhanced and there was a relative skewing toward production of sCD23. These studies implicate the CD40 receptor in the hyperproduction of CD23 and sCD23 in atopic disease and suggest that abnormalities may exist in the cellular pathways leading to sCD23 production.

Nebulized IFN-gamma inhibits the development of secondary allergic responses in mice

The effects of nebulized IFN-gamma on primary and secondary IgE production and development of airway hyper-responsiveness (AHR) were investigated. BALB/c mice received primary exposure to aerosolized OVA daily for 10 days and developed anti-OVA IgE responses, immediate cutaneous reactivity to OVA, and altered airway function when assayed on day 12. After secondary exposure to OVA challenges on days 30 and 31, these mice developed an amplified IgE response, heightened cutaneous reactivity to OVA and AHR when measured on day 37. Administration of IFN-gamma for 13 days, beginning 3 days prior to and during primary OVA sensitization, resulted in a decrease in anti-OVA IgE, increases in serum anti-OVA IgG2a levels, a decrease in cutaneous reactivity to OVA, and normal airway function when assessed on day 12 after primary sensitization. This treatment also prevented the development of secondary anti-OVA IgE responses and altered airway responsiveness but did not induce a secondary rise in anti-OVA IgG2a in the serum measured on day 37. Treatment with IFN-gamma on days 26 to 30, well after primary responses were established but just prior to secondary OVA challenge, abolished the development of secondary anti-OVA IgE responses, resulted in an increase in anti-OVA IgG2a in the serum, and prevented the development of AHR. In vitro, CD4+ T cells obtained from OVA-sensitized mice treated with either "early" or "late" IFN-gamma inhibited IgE production. Delivery of IFN-gamma to the airways can prevent secondary allergen sensitization even after primary sensitization has been achieved and this effect is mediated by CD4+ T cells.

Nebulized IFN-gamma inhibits the development of secondary allergic responses in mice

The effects of nebulized IFN-gamma on primary and secondary IgE production and development of airway hyper-responsiveness (AHR) were investigated. BALB/c mice received primary exposure to aerosolized OVA daily for 10 days and developed anti-OVA IgE responses, immediate cutaneous reactivity to OVA, and altered airway function when assayed on day 12. After secondary exposure to OVA challenges on days 30 and 31, these mice developed an amplified IgE response, heightened cutaneous reactivity to OVA and AHR when measured on day 37. Administration of IFN-gamma for 13 days, beginning 3 days prior to and during primary OVA sensitization, resulted in a decrease in anti-OVA IgE, increases in serum anti-OVA IgG2a levels, a decrease in cutaneous reactivity to OVA, and normal airway function when assessed on day 12 after primary sensitization. This treatment also prevented the development of secondary anti-OVA IgE responses and altered airway responsiveness but did not induce a secondary rise in anti-OVA IgG2a in the serum measured on day 37. Treatment with IFN-gamma on days 26 to 30, well after primary responses were established but just prior to secondary OVA challenge, abolished the development of secondary anti-OVA IgE responses, resulted in an increase in anti-OVA IgG2a in the serum, and prevented the development of AHR. In vitro, CD4+ T cells obtained from OVA-sensitized mice treated with either "early" or "late" IFN-gamma inhibited IgE production. Delivery of IFN-gamma to the airways can prevent secondary allergen sensitization even after primary sensitization has been achieved and this effect is mediated by CD4+ T cells.

Immunoglobulin therapy in Kawasaki syndrome and RSV prophylaxis

Kawasaki syndrome and RSV infection are common illnesses that afflict infants and young children. Recent studies demonstrate that intravenous immunoglobulin (IVIG) treatment significantly reduces the clinical severity of these illnesses. The purpose of the current review will be initially to examine mechanisms of disease pathogenesis in KS and RSV infection. This will be followed by a discussion of the potential mechanisms by which IVIG acts in these two illnesses. In both KS and RSV prophylaxis, an important action by which IVIG may work is primarily through toxin or microbial neutralization resulting in the dampening or prevention of the inflammatory response. Other immunomodulatory actions of IVIG are likely to be operative in these diseases and will be an active area of future research.

Transesophageal echocardiography-guided approach to cardioversion of atrial fibrillation

In patients with atrial fibrillation, electrical cardioversion is often performed to relieve symptoms, to improve left ventricular function, and to decrease thromboembolic risks. However, cardioversion of atrial tachyarrhythmias is associated with an increased embolic risk, with an event rate of up to 5.6%. The American College of Chest Physicians recommend 3 weeks of systemic anticoagulation before elective cardioversion and 4 weeks of systemic anticoagulation afterwards. Expulsion of preexisting left atrial (LA) thrombi with resumption of sinus rhythm has traditionally been considered the mechanism for this increased embolic risk associated with cardioversion. The advent of transesophageal echocardiography (TEE) has allowed accurate detection of LA thrombus. Moreover, recent studies using TEE have identified a state of atrial "stunning" immediately after cardioversion, which is considered a thrombogenic milieu in which new thrombus formation and increased or de novo appearance of LA spontaneous echocardiographic contrast have been observed. Furthermore, embolic events have been reported after cardioversion despite exclusion of preexisting LA thrombus by TEE. These studies strongly suggest an alternative mechanism for embolism after cardioversion, ie, atrial stunning with worsened atrial appendage function and enhanced thrombogenesis. Recent studies have shown the safety of a TEE-guided anticoagulation approach in which exclusion of preexisting LA thrombus by TEE enables early cardioversion without the need for the standard 3 weeks of systemic anticoagulation. The importance of maintaining therapeutic anticoagulation has been further emphasized. Although preliminary observational studies of TEE-guided cardioversion are encouraging, there has been no prospective, randomized trial comparing the two strategies of anticoagulation management. The Assessement of Cardioversion Utilizing Transesophageal Echocardiography (ACUTE) pilot study randomized 126 patients from 10 sites and showed the feasibility and safety of the larger scale study. A larger multicenter, prospective randomized trial is now underway and is expected to randomize a total of 3,000 patients. The results of the ACUTE study will definitively establish the safest and the most cost-effective way to manage anticoagulation for elective cardioversion.

Integrated backscatter for quantification of left atrial spontaneous echo contrast

OBJECTIVES

This study was designed to develop a quantitative method of spontaneous echo contrast (SEC) assessment using integrated backscatter and to compare integrated backscatter SEC measurement with independent qualitative grades of SEC and clinical and echocardiographic predictors of thromboembolism.

BACKGROUND

Left atrial SEC refers to dynamic swirling smokelike echoes that are associated with low flow states and embolic events and have been graded qualitatively as mild or severe.

METHODS

We performed transesophageal echocardiography in 43 patients and acquired digital integrated backscatter image sequences of the interatrial septum to internally calibrate the left ventricular cavity and left atrial cavity under different gain settings. Patients were independently assessed as having no, mild or severe SEC. We compared intensity of integrated backscatter in the left atrial cavity relative to that in the left ventricular as well as to the independently assessed qualitative grades of SEC. Fourier analysis characterized the temporal variability of SEC. The integrated backscatter was compared with clinical and echocardiographic predictors of thromboembolism.

RESULTS

The left atrial cavity integrated backscatter intensity of the mild SEC subgroup was 4.7 dB higher than that from the left ventricular cavity, and the left atrial intensity of the severe SEC subgroup was 12.5 dB higher than that from the left ventricular cavity. The left atrial cavity integrated backscatter intensity correlated well with the qualitative grade. Fourier transforms of SEC integrated backscatter sequences revealed a characteristic dominant low frequency/high amplitude spectrum, distinctive from no SEC. There was a close relationship between integrated backscatter values and atrial fibrillation, left atrial size, left atrial appendage flow velocities and thrombus.

CONCLUSIONS

Integrated backscatter provides an objective quantitative measure of SEC that correlates well with qualitative grade and is closely associated with clinical and echocardiographic predictors of thromboembolism. The relationship between integrated backscatter measures and cardioembolic risk will be defined in future multicenter studies.

In vivo expression of IL-12 and IL-13 in atopic dermatitis

Previous studies in atopic dermatitis (AD) have shown that acute and chronic skin lesions are associated with a TH2-type profile of cytokine expression. IL-12 and IL-13 are recently described cytokines, which possess TH1-and TH2-like actions, respectively. We have used the technique of in situ hybridization to examine the expression of IL-12 and IL-13 messenger RNA in skin biopsy specimens of acute and chronic skin lesions and uninvolved skin from patients with AD. When compared with normal control skin, the acute and chronic skin lesions and unaffected skin from patients with AD had significantly greater numbers of cells that were positive for IL-13 mRNA (p < 0.05). Acute AD skin lesions expressed a higher number of positive cells than those observed in chronic AD skin lesions (p < 0.05) or psoriasis skin lesions (p < 0.05) There was a significant increase in the numbers of IL-12 mRNA-positive cells in chronic skin lesions compared with acute lesions and uninvolved skin from patients with AD (p < 0.05). These data demonstrate that acute AD skin lesions are associated with an increased expression of IL-13 mRNA. In contrast, the relative increase in IL-12 mRNA in chronic AD skin lesions suggests a possible role for IL-12-producing cells in modulating chronic inflammation.

Bacterial superantigens induce V beta-specific T cell receptor internalization

Staphylococcal enterotoxins can cause toxic shock syndrome and autoimmune diseases. Circulating T cells from these diseases have a very wide range of expression in particular T cell receptor (TCR) beta chain variable regions (V beta). One possibility for this wide range of TCR V beta expression is that during acute infection with organisms secreting superantigens (SAg) these potent molecules might modulate TCR expression. To test this hypothesis, we investigated the potential effects of SAg on TCR V beta cell surface expression. Peripheral blood mononuclear cells (PBMC) from healthy donors were incubated with staphylococcal SAg. Toxic shock syndrome toxin-1 (TSST-1) induced downregulation of V beta 2 expression, whereas staphylococcal enterotoxin (SE) B induced V beta 3-and V beta 12-specific downregulation. TSST-1 did not interfere with anti-V beta 2 mAb binding. Therefore, this downregulation was not due to steric hindrance of Ab binding by TSST-1. TSST-1 induced V beta 2 downregulation was time-, dose- and temperature-dependent. CD3 expression decreased in parallel with reduction of V beta expression. CD4 and CD8 expression were only slightly decreased. CD2, CD25 and HLA-DR expression were upregulated following TSST-1 stimulation of T cell lines. To investigate the fate of TCR after toxin stimulation, V beta 8+ Jurkat T cells were incubated with SEE which is known to stimulate V beta 8+ T cells, and analysed with fluoresence microscopy, and immunoprecipitation and Western blotting. After SEE stimulation, there was an increase in V beta 8 molecules found in the cytoplasm which correlated with loss of cell surface V beta 8 molecules, suggesting internalization of cell surface V beta 8 molecules was induced by SEE stimulation. Shedding of V beta 8 molecules into the culture supernatant was not detected. These data demonstrate that SAg mediated downregulation of TCR expression occurs primarily as the result of TCR internalization. This downregulation phenomenon may have physiological and pathological consequences in patients infected with Staphylococcus aureus.

Candida albicans induces selective expansion of human T lymphocytes expressing the T-cell receptor variable region V beta 5.1

Candida albicans is a common pathogen which can present major problems as an opportunistic skin pathogen in patients with immunodeficiency. The exact nature of the T cell responses to C. albicans is poorly understood. The purpose of this study was to determine whether C. albicans could stimulate the selective expansion of T lymphocytes expressing particular V beta gene segments. Human T lymphocytes stimulated in vitro with an extract of C. albicans were analyzed for T cell receptor V beta gene expression by using a quantitative PCR technique. We found that stimulation of peripheral blood mononuclear cells (PBMC) produced a selective increase in the expression of V beta 5.1 and 5.2 gene transcripts. Using cytofluorographic analysis with available anti-V beta monoclonal antibodies, we verified that there was a significant selective expansion (P = 0.035) of V beta 5.1 positive T lymphocytes in PBMC from six subjects stimulated in vitro with C. albicans. PCR analysis of V beta 5.1 expansion in 10 subjects showed increases in V beta 5.1 gene transcripts in 7/10 subjects. More importantly, analysis of the T cell infiltrate 48 h after intradermal injections with C. albicans also showed significant expression of V beta 5.1 in the infiltrates, along with the infiltration of V beta 8.1 + T cells. The selective expansion of V beta 5.1 bearing T lymphocytes in PBMC stimulated with C. albicans and in skin test reactions to C. albicans suggests that a restricted population of T cells react to C. albicans. Furthermore, our present data raise the provocative possibility that one or more antigens in C. albicans can act as a superantigen, producing selective expansion of a population of T lymphocytes bearing a particular V beta specificity.

Differential effects of staphylococcal toxic shock syndrome toxin-1 on B cell apoptosis

Superantigens, such as toxic shock syndrome toxin 1 (TSST-1), have been implicated in the pathogenesis of several autoimmune and allergic diseases associated with polyclonal B cell activation. In this report, we studied the in vitro effects of TSST-1 on B cell activation. We show herein that TSST-1 produced antagonistic effects on Ig synthesis by peripheral blood mononuclear cells (PBMC) from normal subjects, depending on the concentration used; Ig production was inhibited at 1000 pg/ml (P < 0.01) and enhanced at 1 and 0.01 pg/ml (P < 0.01) of toxin. Cultures of PBMC were then examined for morphologic features and DNA fragmentation characteristic for apoptosis. B cells exhibited a significantly higher (P < 0.01) incidence of apoptosis after stimulation with 1000 pg/ml of TSST-1 compared with 1 or 0.01 pg/ml of toxin or medium alone. Abundant expression of Fas, a cell surface protein that mediates apoptosis, was detected on B cells after stimulation with 1000 pg/ml of TSST-1 and was significantly higher on B cells undergoing apoptosis than on live cells (P = 0.01). Additionally, increased Fas expression and B cell death occurred at concentrations of TSST-1 inducing the production of high amounts of gamma interferon (IFN-gamma), and both events could be blocked by neutralizing anti-IFN-gamma antibody. These findings suggest that high concentrations of TSST-1 can induce IFN-gamma-dependent B cell apoptosis, whereas at low concentrations it stimulates Ig synthesis by PBMC from normal subjects. These findings support the concept that staphylococcal toxins have a role in B cell hyperactivity in autoimmunity and allergy.

Kawasaki syndrome: immunomodulatory benefit and potential toxin neutralization by intravenous immune globulin

Kawasaki Syndrome (KS) is an acute multi-system vasculitis of infancy and early childhood associated with the development of coronary artery abnormalities. The prevalence of cardiovascular abnormalities can be significantly reduced by treating patients during the first 10 days of illness with high-dose intravenous immune globulin (IVIG). Despite the widely held belief that KS is caused by an infectious agent, the aetiology of this illness remains controversial. Recent immunological and microbiological studies suggest a potential role for staphylococcal and streptococcal toxins (superantigens) in the pathogenesis of KS. Confirmation of these findings could result in more effective diagnostic and therapeutic approaches for the treatment of this common cause of acquired heart disease in children.

Cutaneous exposure to the superantigen staphylococcal enterotoxin B elicits a T-cell-dependent inflammatory response

We analyzed the impact of superantigens secreted by skin-colonizing Staphylococci on the skin and the associated lymphoid tissue following epicutaneous application and intracutaneous injection of small amounts of staphylococcal enterotoxin B (SEB). A single intracutaneous injection of 50 ng of SEB elicited a strong inflammatory response in the skin of BALB/c mice. Three to 6 h later, we observed langerhans cell activation, mast cell degranulation, vasodilation, upregulation of ICAM-1, and induction of VCAM-1 on dermal blood vessels, with vascular adhesion of granulocytes. by 12 to 24 h, cell infiltration of the dermis increased, reaching the epidermis. Among the infiltrating leukocytes, a substantial number of eosinophils was found. After 48 h, the infiltrate was dominated by mononuclear cells. The response to SEB was dose-dependent, and signs of inflammation slowly disappeared over 5 to 7 days. Although the induction of VCAM-1 on dermal blood vessels suggested a role for interleukin-1/tumor necrosis factor-alpha in this reaction, the activation of monocytes/macrophages was not able to substitute for lymphocytes, as severe combined immunodeficiency (SCID) mice (which are lymphocyte-deficient) did not mount an inflammatory skin response to intradermal injection of SEB. The fact that nude mice (T-cell-deficient) also did not mount an inflammatory response to SEB indicated the T-cell dependency of the response. The V beta specificity of the SEB effect was demonstrated by the fact that SJL/J mice, which lack V beta 8+ T cells (the major SEB-reactive T cell population in mice), exhibited much weaker responses. Deletion or tolerization of SEB-reactive V beta T cells was not observed after a single intradermal injection of such minute amounts of SEB.