Immunophenotyping of the cutaneous infiltrate and of the mononuclear cells in the peripheral blood in patients with atopic dermatitis

T-Helper Type 2 Cells Direct Antigen-Induced Eosinophilic Skin Inflammation in Mice

Eosinophilic inflammation in combination with immunoglobulin E (IgE) production is a characteristic feature of atopic dermatitis. Although activated T-helper type (Th) 2 cells play critical roles in the local accumulation and activation of eosinophils, whether they induce eosinophilic skin inflammation, independent of the IgE-mediated pathway has been unclear. To address the functional role of T cells in allergic skin diseases, we herein transferred Th1/Th2-differentiated or naive DO11.10 T cells into unprimed BALB/c mice. Ovalbumin-specific Th2 cells, as well as eosinophils, accumulated in the skin upon antigen challenge, despite the absence of antigen-specific IgE. Neither antigen-specific Th1 nor naive T cells induced eosinophil accumulation, although Th1 cells by themselves migrated into the skin. Interleukin (IL)-4, IL-5, and eotaxin were specifically produced in the skin of antigen-challenged, Th2 cell-transferred mice, whereas interferon (IFN)-γ and regulated on activation, normal T cell expressed and secreted (RANTES) were preferentially produced in Th1 cells-transferred mice. Production of monocyte chemoattractant protein (MCP)-1 and MCP-3 was enhanced by both Th1 and Th2 cells. The accumulation of eosinophils and Th2 cells in the skin was suppressed by both dexamethasone and FK506, indicating an essential role of Th2 cells in eosinophil recruitment. We conclude that Th2 cells can induce eosinophilic infiltration into the skin in the absence of antigen-specific IgE.

Pollen Grains Induce a Rapid and Biphasic Eczematous Immune Response in Atopic Eczema Patients

INTRODUCTION

Eczematous reactions to type I allergy-inducing antigens are documented in a subgroup of patients with atopic eczema. Yet, the underlying immunological mechanisms are not well understood.

MATERIAL AND METHODS

To delineate the effect of native pollen grains on human skin of healthy and atopic individuals we performed patch tests (atopy patch test with native pollen grains, PPT). Nickel patch tests (NPT) served as an established model of contact dermatitis. Skin site biopsies were taken 6-96 h after allergen application and investigated immunohistochemically.

RESULTS

Histology of positive patch tests showed an influx of mononuclear cells (predominantly CD4+, CD25+, CD45RO+). This influx was detected earlier in the PPT reaction than in the immune response to nickel. A biphasic cytokine response could be detected in the PPT: IL-5 dominated in the early, IFN-gamma in the late phase. The NPT was continuously dominated by IFN-gamma. Dendritic cell subpopulations imitated the earlier kinetics of the mononuclear infiltrate.

DISCUSSION

Thus, pollen grains induce eczematous reactions in susceptible individuals. This reaction appears clinically and immunohistochemically similar to the contact hypersensitivity reaction to nickel but follows a faster kinetic and a biphasic course: Th2 and IgE in the early (24 h) and Th1 predominance in the late (96 h) phase.

Increase in macrophage migration inhibitory factor levels in lacrimal fluid of patients with severe atopic dermatitis

BACKGROUND AND AIMS OF THE STUDY

Atopic dermatitis is a chronic inflammatory skin disorder that often involves some ophthalmic features. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is associated with the generation of cell-mediated immune responses. Although serum MIF levels may be elevated in severe atopic dermatitis, the quantity of MIF in regional ocular fluid remains unknown. We measured MIF levels in tears (lacrimal fluid) of patients with atopic dermatitis.

PATIENTS AND METHODS

Tear samples were collected from 16 patients with atopic dermatitis, 10 patients with allergic conjunctivitis, and 15 healthy control subjects. The clinical severity of atopic dermatitis was evaluated according to the Scoring Atopic Dermatitis (SCORAD) index. The index was calculated by summing the following scores: extent criteria, intensity criteria, and subjective symptoms. Macrophage migration inhibitory factor levels were determined by a human MIF enzyme-linked immunosorbent assay. All comparisons were two-tailed, and P values <0.01 were considered as statistically significant.

RESULTS

The mean MIF concentration in lacrimal fluid collected from healthy control subjects was 0.69+/-0.2 ng/ml. The mean tear MIF levels were 17.87+/-6.3 ng/ml in moderate-to-severe atopic dermatitis (SCORAD> or =15, P=0.002), 0.93+/-0.08 ng/ml in mild atopic dermatitis (SCORAD<15), and 2.76+/-0.86 ng/ml in allergic conjunctivitis (P=0.008).

CONCLUSIONS

A proinflammatory cytokine MIF level was elevated in tears as well as serum in cases of severe atopic dermatitis. These results suggest that MIF may play an important role in the induction or enhancement of ophthalmic features related to severe atopic dermatitis.

Corticosteroids But Not Pimecrolimus Affect Viability, Maturation and Immune Function of Murine Epidermal Langerhans Cells

Given the importance of dendritic cells in the immune response, we investigated the effect of corticosteroids (CS) on the integrity, survival, and function of murine Langerhans cells (LC) in comparison with pimecrolimus, a novel anti-inflammatory drug for the topical treatment of atopic dermatitis. BALB/c mice were treated twice on one day with ethanolic solutions of the compounds. At 24-72 h after the last application, we observed fragmented DNA, caspase-3 activity, and an upregulation of CD95 expression in LC from mice treated with CS but not in LC of pimecrolimus- or vehicle-treated animals. CS-epidermal cell (EC) supernatants but not pimecrolimus-EC supernatants contained significantly lower amounts of soluble factors (GM-CSF, TNF-alpha, IL-1alpha) required for LC survival and maturation than EC supernatants from vehicle-treated mice. With regard to LC maturation, CS but not pimecrolimus inhibited the expression of CD25, CD205, and costimulatory molecules. In line with this, LC from pimecrolimus-treated mice were similar to LC from vehicle-treated mice in their capacity to stimulate antigen-presenting function and migration, whereas LC from CS-treated mice were greatly impaired in these abilities. In summary, our data show for the first time that CS but not pimecrolimus induce apoptosis in LC in situ, implying that the prolonged use of CS could have adverse effects on the skin immune system.

Response to Malassezia pachydermatis by peripheral blood mononuclear cells from clinically normal and atopic dogs

OBJECTIVE

To investigate the potential cell-mediated immune response of atopic dogs to the yeast Malassezia pachydermatis and to correlate it with the type-1 hypersensitivity (humoral) response of the same population of dogs.

ANIMALS

16 clinically normal dogs, 15 atopic dogs with Malassezia dermatitis, 5 atopic dogs with Malassezia otitis, and 7 atopic control (ie, without Malassezia dermatitis or otitis) dogs.

PROCEDURE

A crude extract of M pachydermatis was extracted for use as an intradermal allergy testing reagent and for stimulation of isolated peripheral blood mononuclear cells in vitro. Flow cytometry was also used to assess cell surface antigenic determinants (CD3, CD4, CD8, CD14, CD21, CD45RA, surface immunoglobulin) on peripheral blood mononuclear cells.

RESULTS

Atopic dogs with cytologic evidence of Malassezia dermatitis had an increased lymphocyte blastogenic response to crude M pachydermatis extract, compared with clinically normal dogs and dogs with Malassezia otitis. Atopic control dogs did not differ significantly in their responses from atopic dogs with Malassezia dermatitis or otitis. A significant correlation was not found between the lymphocyte blastogenic response and the type-1 hypersensitivity response to M pachydermatis within any of the groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Cell-mediated and humoral reactivities to M pachydermatis contribute to the pathogenesis of atopic dermatitis in dogs but are not directly correlated. Modification of the dysregulated immune response toward M pachydermatis may assist in the reduction of pathologic changes associated with an atopic dermatitis phenotype in dogs.

Potent costimulation of effector T lymphocytes by human collagen type I

Purified, resting peripheral blood T lymphocytes were previously reported to undergo beta(1) integrin-dependent activation when cultured with anti-CD3 mAb coimmobilized with fibronectin, but not type I collagen. However, the extravascular T cells that encounter immobilized extracellular matrix proteins and are involved in disease pathogenesis have different properties from resting peripheral blood cells. In this study, we confirm that resting CD4(+) and CD8(+) T cells from peripheral blood are costimulated by immobilized fibronectin, but not type I collagen. In contrast, Ag- or mitogen-stimulated CD4(+) and CD8(+) T cell lines, used as models of the effector cells involved in disease, are more potently costimulated by type I collagen than fibronectin. The collagen-induced effects are similar in assays with serum-free medium and in more physiological assays in which anti-CD3 mAb is replaced by a threshold concentration of Ag and irradiated autologous PBMC as APC. The responses are beta(1) integrin dependent and mediated largely by very late Ag (VLA) 1 and 2, as shown by their up-regulation on the T cell lines as compared with freshly purified resting PBL, and by the effects of blocking mAb. Reversed phase HPLC located the major costimulatory sequence(s) in the alpha1 chain of type I collagen, the structure of which was confirmed by amino acid sequencing. The results demonstrate the potential importance of type I collagen, an abundant extracellular matrix protein, in enhancing the activation of extravascular effector T cells in inflammatory disease, and point to a new immunotherapeutic target.

T cell stimulating stratum corneum antigens: characterization by chromatography and electrophoresis indicates limited diversity

As part of a search for T cell autoantigens in inflammatory skin diseases, we have demonstrated proteinase K sensitive, denaturation stable, T cell stimulatory material with antigenic properties in aqueous extracts of stratum corneum from normal human skin. Activity was also demonstrable in extracts of whole epidermis. A combination of preparative, analytical, and microbore reversed phase high performance liquid chromatography, chromatofocusing, and denaturing preparative sodium dodecylsulfate-polyacrylamide gel electrophoresis indicated limited structural diversity. Five components were separated, with Mr values from 5 to 18 kDa and apparent PI values from 4.5 to 10. Three components were purified to near homogeneity and showed molecular weights of 5, 13.5, and 18 kDa. Their potency was shown by the ability to induce stimulation indices of 20-89 with peripheral blood mononuclear cells and >500 with T cell lines. Use of inhibitors indicated that the active materials were not generated by the in vitro actions of proteases during extraction. The five partially purified components induced a time course of peripheral blood mononuclear cell proliferation compatible with the effects of antigen rather than superantigen. The 5 kDa component was rigorously bulk purified to yield a fraction that induced potent T cell activation but contained minimal detectable protein, a further indication of its biologic potency. Normal stratum corneum thus contains previously undescribed T cell antigens of high potency but limited structural diversity. The present data form a basis for determining their structure, cellular origin, and pathogenic relevance.

Increased production of macrophage migration inhibitory factor by PBMCs of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic pruritic inflammatory skin disorder. The underlying cause of AD is multifactorial, and several cytokines are considered to be involved in this severe inflammatory skin disease. Macrophage migration inhibitory factor (MIF) is an immunoregulatory cytokine essential for T-cell activation and delayed-type hypersensitivity. Recently we demonstrated that serum MIF content was significantly elevated in patients with AD. Consistent with this, expression of MIF messenger RNA in keratinocytes of the eczematous skin lesion was up-regulated.

OBJECTIVE AND METHOD

Although keratinocytes are considered to be a potential source of increased serum MIF content in AD, precise evaluation has not been carried out in other tissues. MIF is ubiquitously expressed in various cells, including T cells and macrophages. In this study we examined MIF production and its messenger RNA level of PBMCs from patients with AD to investigate the contribution of these cells to elevated serum MIF content and to its pathologic characteristics.

RESULTS

Consistent with our previous findings, the serum MIF content of patients with AD was significantly elevated compared with nonatopic healthy control subjects and patients with chronic urticaria without eczema. As for the MIF productivity of unstimulated PBMCs, the MIF content in the culture medium of PBMCs obtained from patients with AD (40.4 +/- 8.4 ng/mL) (mean +/- SEM) was significantly increased compared with that from healthy control subjects (6.6 +/- 1.1 ng/mL) and patients with chronic urticaria (8.5 +/- 1.4 ng/ml) (P <.0001). When PBMCs were stimulated by concanavalin A, MIF production by PBMCs of patients with AD was more enhanced than in control subjects or patients with chronic urticaria. The increased ratio of MIF production by PBMCs in response to concanavalin A was significantly correlated with the severity of clinical features of AD. Supporting these results, the level of MIF mRNA in PMBCs of patients with AD was significantly higher than in nonatopic healthy control subjects.

CONCLUSIONS

The current results showed that PBMCs should be an important source of increased serum MIF in AD. Because MIF has the potential to induce local and systemic inflammatory and immune responses, it is conceivable that MIF produced by PBMCs may affect local and systemic pathologic features in AD.

Increased numbers of CD4+ and CD8+ T cells in lesional skin of cats with allergic dermatitis

The aim of this study was to characterize T cells in the skin of cats with an allergic dermatitis histologically compatible with atopic dermatitis, since T cells play an important role in the pathogenesis of atopic dermatitis in humans. We observed a significantly greater number of T cells in lesional skin of domestic short-haired cats with allergic dermatitis (n = 10; median age 5.8 years) than in the skin of healthy control animals (n = 10; median age 5.0 years). In the skin of the healthy control animals, one or two CD4+ cells and no CD8+ cells were found. A predominant increase of CD4+ T cells and a CD4+/CD8+ ratio (mean +/- SD: 3.9 +/- 2.0) was found in the lesional skin of 10 cats with allergic dermatitis. The CD4+/CD8+ cell ratio in the skin of healthy control animals could not be determined because of the absence of CD8+ cells. The CD4+/CD8+ cell ratio in the peripheral blood of 10 cats with allergic dermatitis (mean +/- SD: 1.9 +/- 0.4) did not differ significantly from that in 10 healthy control animals (2.2 +/- 0.4). The CD4+/CD8+ cell ratio and predominance of CD4+ T cells in the lesional skin of cats with allergic dermatitis is comparable to that found in atopic dermatitis in humans. In addition, the observed increase of CD4+ T cells in the nonlesional skin of cats with allergic dermatitis compared to the skin of healthy cats is similar to what is seen in humans. Cytokines produced by T cells and antigen-specific T cells are important mediators in the inflammatory cascade resulting in atopic dermatitis in humans. This study is a first step to investigate their role in feline allergic dermatitis.

Potent T cell stimulatory material with antigenic properties in stratum corneum of normal human skin

T cell mediated autoimmunity may be important in inflammatory skin disease, but target autoantigens have not previously been described. In studies aimed at defining T cell epitopes, aqueous extracts of normal facial and plantar stratum corneum have consistently been found to induce potent proliferation of peripheral blood mononuclear cells from normal donors and patients with inflammatory skin disease, giving stimulation indices up to 80. Potent stimulation was seen with both autologous and allogeneic stratum corneum extracts. Because of the presence of inhibitory material, demonstration of the stimulatory activity was critically dependent on extract concentration, and was facilitated by short-term pulsing of cultures with extract. The proliferation of cells purified from peripheral blood mononuclear cells by immunomagnetic beads and immunophenotyping of cell lines generated from peripheral blood mononuclear cells, confirmed the T cell nature of the response to stratum corneum extracts. The activity was inhibited by HLA-DR monoclonal antibody, indicating the presence of antigen or superantigen. Tetanus toxoid reactive clones and a purified protein derivative reactive line failed to respond to the stratum corneum extracts, indicating that the active material is not a nonspecific T cell stimulant such as a cytokine or mitogen. This and the failure of recombinant interleukin-1alpha to stimulate peripheral blood mononuclear cells in concentrations up to 1000 U per ml, indicate that the activity is not due to interleukin-1. We propose the hypothesis that antigenic or superantigenic material is normally sequestered from the immune system in the epidermis, but induces T cell activation when released following wounding and in disease, and that this represents an important and previously unrecognized pathogenic mechanism.

A human-SCID mouse model for allergic immune response bacterial superantigen enhances skin inflammation and suppresses IgE production

Chronic skin colonization with Staphylococcus aureus is a well-known feature in atopic dermatitis. The aim of this study was to develop a human-SCID mouse model to analyze the possible role of bacterial superantigens in human allergic immune responses under in vivo conditions. SCID mice were reconstituted with peripheral blood mononuclear cells (between 2 and 9 x 10(7) cells per mouse) from atopic dermatitis patients sensitized to house dust mite allergen (Der p). Total and Der p specific antibody production required the following conditions: (i) injection of Der p; (ii) presence of CD14+ antigen-presenting cells; and (iii) IL-4 as shown by the inhibitory effect of human soluble IL-4 receptor on immunoglobulin E production. This model was used to study the immunomodulatory effects of the superantigen staphylococcal enterotoxin B in comparison with Der p. In intraperitoneally reconstituted human-SCID mice, topical treatment was ineffective in inducing skin inflammation. Therefore, additionally to intraperitoneal transfer, peripheral blood mononuclear cells from atopic donors were also injected intradermally. Such reconstituted SCID mice were then exposed via the skin to either Der p, staphylococcal enterotoxin B, or a combination of both. Maximal effects on epidermal inflammation and dermal T cell infiltration were obtained with staphylococcal enterotoxin B and Der p. Staphylococcal enterotoxin B alone was less effective and Der p only stimulated dermal T cell infiltration. These findings support the hypothesis that bacterial superantigens can act as trigger factors in allergic skin inflammation.

Macrophage migration inhibitory factor is an essential immunoregulatory cytokine in atopic dermatitis

Macrophage migration inhibitory factor (MIF) is one of the immunoregulatory cytokines involved in T-cell activation and delayed-type hypersensitivity. To elucidate involvement of this cytokine in the pathogenesis of atopic dermatitis (AD), we examined serum MIF concentrations of patients with AD and non-atopic normal healthy individuals. The mean serum MIF concentration of the AD patients (n = 36) was 36.4 +/- 3.7 ng/ml (mean +/- SEM), whereas that of the non-atopic dermatitis patients (n = 17) or healthy individuals (n = 61) were 13.1 +/- 1.8 or 6.5 +/- 0.45 ng/ml, respectively. Accordingly, immunohistochemistry of the inflammatory skin lesion of an AD patient demonstrated that MIF protein was diffusely expressed throughout the whole epidermal layer. After 4-week steroid ointment treatment, the MIF concentration decreased as clinical symptoms improved. The serum level of TNF-alpha was also decreased in parallel with that of MIF. Considering the T-cell dysfunction and disordered cytokine-network reported in AD, it was strongly suggested that MIF was a critical protein for immunoregulation in the pathophysiological mechanism of AD. In this context, MIF may become a useful laboratory parameter to comprehend the clinical course of the disease.

Characterization of the cutaneous inflammatory infiltrate in canine atopic dermatitis

Sections from lesional atopic, clinically normal atopic, and normal canine skin were investigated by light microscopy and an immunoperoxidase method using monoclonal antibodies specific for canine leukocyte antigens. We confirmed that skin-infiltrating cells of canine atopic dermatitis are constituted of mast cells, dendritic antigen-presenting cells, memory helper T-lymphocytes, low numbers of eosinophils and neutrophils, and rare B-lymphocytes. The presence of epidermal eosinophil microaggregates and clustered Langerhans' cells supports the hypothesis of epidermal allergen contact. The hyperplasia of epidermal T-cells expressing the gamma/delta T-cell receptor appears specific to canine atopic dermatitis compared with its human counterpart. This finding could be explained by an interspecies difference in skin immune systems or, alternatively, by an active participation of these epitheliotropic gamma/delta T-cells in the cutaneous allergic immune response in dogs. The paucity of dermal neutrophils in spontaneous lesions of canine atopic dermatitis is notably different from the neutrophil-rich late-phase reactions provoked by intradermal allergen injections in allergic dogs. This difference in the cellular infiltrate probably results from variations in the immune reaction between single and repeated allergen exposure as well as epidermal versus dermal antigen contact.

Monitoring of disease activity by measurement of inflammatory markers in atopic dermatitis in childhood

Serum levels of soluble interleukin-2 receptor (sIL-2R), intercellular adhesion molecule-1 (ICAM-1), endothelial leukocyte adhesion molecule (ELAM-1), and eosinophil cationic protein (ECP) were measured in 20 patients with atopic dermatitis before and after 4 days' treatment with prednisolone p.o. as well as in 16 healthy, nonatopic controls. Before steroid treatment, patients with atopic dermatitis demonstrated significantly higher serum levels of sIL-2R, ICAM-1, and ECP than healthy controls (P < 0.001), whereas ELAM-1 levels were not different between the groups. After 4 days of steroid treatment, clinical improvement was associated with a decrease of sIL-2R (P < 0.003), ICAM-1 (P < 0.004), and ECP serum levels (P < 0.003), but ELAM-1 levels remained unchanged. Both serum ECP and sIL-2R levels were significantly correlated with disease severity before as well as after steroid treatment. Changes of sIL-2R concentrations were strongly related to the changes of ECP levels. In addition, changes of serum sIL-2R and ECP levels in percentage were correlated with clinical improvement. These results indicate that the determination of sIL-2R and ECP serum levels may be useful in monitoring disease activity in atopic dermatitis in childhood, especially in treatment trials.

Immunophenotyping of skin-infiltrating T-cell subsets in dogs with atopic dermatitis

Atopic dermatitis in dogs has many clinical features that are identical to those of the same disorder in man. To investigate the pathogenesis of this disease in dogs and the possibility of similarities to the pathogenesis in humans we compared the presence and ratio of CD4+ and CD8+ T-cells in the cutaneous infiltrate of lesional and non-lesional skin of atopic dogs with that in the skin of healthy dogs. In ten dogs with atopic dermatitis and ten healthy dogs the skin was biopsied at the predilection sites for atopic dermatitis and histological sections were immunohistochemically stained for CD4 and CD8. The staining showed an increase in CD4+ and CD8+ T-cells in canine lesional atopic skin, with a predominance of CD4+ T-cells in the epidermis. In non-lesional atopic skin there was also an infiltration with CD4+ and CD8+ T-cells, but without predominance of CD4+ T-cells. The results in the separate predilection sites did not differ substantially from the mean results. These observations indicate further similarities in the immunopathogenesis of atopic dermatitis in dogs and humans, which may have consequences for the control of atopic dermatitis in dogs and contributes to a possible role of the dog as a model for human atopic dermatitis.

The chemotactic activity of T-lymphocytes in response to interleukin 8 is significantly decreased in patients with psoriasis and atopic dermatitis

Involvement of T-lymphocytes in the pathogenesis of psoriasis and atopic dermatitis is well established. The question arises as to whether not only tissue infiltrating but also circulating T-lymphocytes are involved in the disease process. Therefore we sought to determine whether T-lymphocytes from patients with psoriasis and atopic dermatitis show abnormal biological behavior to the proinflammatory chemokine interleukin 8 (IL-8) in vitro as studied by their chemotactic activity. In addition, the expression of T-cell activation markers such as HLA-DR and interleukin 2 receptor (IL-2R) were analysed with FACS-technique. In all, 25 patients with psoriasis (13 patients with severe psoriasis and 12 patients with mild psoriasis) and 11 patients with atopic dermatitis were investigated. For comparison. T-lymphocytes from 14 healthy controls were tested equally. The results show that T-cell chemotactic responses to IL-8 were significantly decreased in patients with severe psoriasis as compared to healthy controls. T-cells from patients with atopic dermatitis demonstrated an even more pronounced decrease in chemotactic response as compared to T-cells from psoriasis patients or healthy controls. In contrast, increased expression of activation markers HLA-DR and IL-2R were demonstrated in circulating T-cells from patients with severe psoriasis and atopic dermatitis in comparison to healthy controls. It can be concluded that circulating T-cells in patients with severe psoriasis and atopic dermatitis show a decreased in vitro chemotactic response to IL-8. Furthermore, the in vivo phenotypic activation state of T-lymphocytes in these patients seemed to be associated with their decreased in vitro functional capacity.

Serum levels of eosinophil cationic protein reflect the state of in vitro degranulation of blood hypodense eosinophils in atopic dermatitis

In patients with atopic dermatitis (AD), serum levels of eosinophil cationic protein (ECP) have been shown to be a good reflector of disease severity. To elucidate what serum levels of ECP actually reflect, ECP levels in serum and plasma and cytological aspects of blood eosinophils were examined in AD patients (n = 27) and compared to healthy subjects (n = 12). Significantly elevated levels of serum ECP were noted in AD patients, while plasma ECP were uniformly recorded at nadir levels in both AD patients and normal subjects. In addition to blood eosinophilia, AD patients had significantly increased numbers of hypodense eosinophils (HEo) with morphological characteristics consistent with an activated state. Serum ECP levels strongly correlated with HEo numbers rather than with total eosinophil counts. These results indicate that elevated levels of serum ECP may be a consequence of in vitro degranulation of "activated" HEo, not of ECP supplementation from lesional skin. In addition, the dynamic correlations of eosinophil-associated parameters (total eosinophil counts, HEo numbers, and serum ECP levels) with AD severity suggest that inflammatory events in lesional skin may be involved in causing not only eosinophilopoiesis in bone marrow, but also development of HEo in the periphery, whose degree in turn may be mirrored in the levels of serum ECP in vitro.

Growth of herpes simplex type 1 on skin explants of atopic eczema

In a novel approach to looking at why some children with atopic eczema are susceptible to cutaneous herpes simplex virus (HSV) infections, this study evaluates the hypothesis that HSV replicates more easily on eczematous than normal skin. Growth of HSV on eczematous skin explants was compared with growth on explants from three control groups (psoriasis, Darier's disease and normal skin) over a 2-day period. Growth of HSV was significantly less on normal skin than in atopic eczema, psoriasis and Darier's disease. Virus replicated more quickly, and grew to higher titre within 24h, in eczematous and psoriatic explants than in normal skin. A defect in skin barrier function and host defence factors including local cytokine secretion are discussed as possible mechanisms in causing the increased susceptibility of children with atopic eczema to HSV infection.

Murine animal models to study the central role of T cells in immediate-type hypersensitivity responses

The development of allergic sensitization and inflammation is dependent on activation and stimulation of T cells that exhibit pro-allergic functions. A mouse model system was developed to study the role of T cells in allergic sensitization in more detail. Local sensitization of mice stimulates an allergen specific IgE/IgG1 response that is associated with the development of immediate type skin test responses and increased airway responsiveness (AR). Strains of mice are identified that are high or low responder animals for allergens including ovalbumin and house dust mite. Each allergen stimulates a different pattern of T-cell receptor V beta expressing T cells in local draining lymph nodes. To induce a state of increased AR, at least two separate events are required. The first event is the presence of allergen specific IgE/IgG1. The second event is characterized as a local allergen challenge at the site of the response. These T cells play a critical role in the regulation of the allergic immune response including IgE production and increased AR. Based on these results intervention strategies can be developed which specifically target the development and function of these allergen specific T-cell populations and modify their pro-allergic activities.

[Treatment of atopic dermatitis]

There are three components in the treatment of atopic dermatitis: 1) a general treatment (mainly antibiotherapy directed towards Staphylococcus aureus during acute phases), 2) local treatment (local antiseptics, local steroids, emollients), 3) practical advice. In addition, it is of great importance that clear and complete information on the illness should be given to the parents.

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.

IgE, IgE receptors, and other immunocytochemical markers in atopic and nonatopic patients with vernal keratoconjunctivitis

BACKGROUND

Vernal keratoconjunctivitis (VKC) often is associated with atopy but a considerable part of the patients lack evidence of specific hypersensitivity. An immunocytochemical study was undertaken with the aim of detecting possible differences in the tissue inflammatory response between atopic and nonatopic subjects with VKC.

METHODS

Conjunctival biopsy specimens from six atopic and three nonatopic subjects with VKC (age range, 7-17 years) and eight healthy control subjects (age range, 3-15 years) were analyzed with a panel of monoclonal and polyclonal antibodies.

RESULTS

No distinct differences in cell counts between atopic and nonatopic subjects with VKC were observed. Vernal keratoconjunctivitis specimens as a whole showed higher counts than control specimens for CD3+, CD4+, HLA-DR+, CD38+, EG2+, CD68+, IgE+, FC epsilon RI+, IgA+, IgG+, and IgM+ cells in the substantia propria; and for CD1a+, IgE+, and EG2+ cells in the epithelium.

CONCLUSIONS

Because the number of cells expressing CD4, EG2, IgE, and the high-affinity receptor for IgE, all of which are considered relevant in infiltrates of allergic conditions, were similar in atopic and nonatopic subjects, the authors conclude that the role of allergen-specific IgE sensitization in the pathogenesis of VKC remains unclear.

Treatment of severe atopic dermatitis with extracorporeal photopheresis

Extracorporeal photopheresis using UVA irradiation of enriched lymphocytes in the presence of 8-methoxypsoralen (8-MOP) as a photoactivatable substrate has been employed for the treatment of several immunologically mediated disorders. We report on the first three patients subjected to extracorporeal photopheresis for severe atopic dermatitis. All patients had a lifelong history of atopic skin inflammation, and their disease had finally become resistant to well-established therapeutic regimes. Extracorporeal photopheresis resulted in a marked clinical improvement in the skin lesions of all patients. The decrease in cutaneous inflammatory activity became evident by the end of the second photopheresis cycle. In two patients skin lesions had virtually disappeared after the fifth treatment cycle, while in the third patient a lasting and substantial improvement in pruritus and erythema was achieved. Clinical remission was stable under maintenance therapy with prolonged intervals between photopheresis sessions. Therapeutic efficacy was reflected by a marked reduction in IgE serum levels in all three patients, while serum concentration of IgG, IgM and IgA as well as the profile of circulating lymphocytes remained essentially unchanged. No clinical signs of immunosuppression or other severe adverse events became evident. Collectively, our preliminary results indicate that extracorporeal photopheresis may interfere with the pathomechanisms leading to atopic dermatitis and therefore should be considered as a treatment modality for severe forms of this recalcitrant disorder.

Idiopathic CD4+ lymphocytopenia associated with chronic pruritic papules

This is a case report and family study of a 65-year-old man with chronic prurigo lesions, in whom we demonstrated a selective deficiency of circulating T-helper/inducer lymphocytes (CD4+), in the absence of any apparent predisposing disease. He is seronegative for human immunodeficiency virus (HIV types 1 and 2) and human T-cell lymphotropic virus (HTLV-I and HTLV-II), and fulfils the criteria for the syndrome of idiopathic CD4+ T lymphocytopenia. He has an atopic diathesis, has had a severe adult chickenpox infection, chronic staphylococcal infections, tinea pedis and recalcitrant warts. He has also suffered from respiratory infections, for which no specific aetiological agent has been identified. His peripheral total lymphocyte count has been persistently abnormal since it was first measured in 1969. He has a marked CD4+ T-cell lymphocytopenia. His son, who does not have any skin disorder, has a low CD4+ T-cell count.

Atopic dermatitis: recent trends in pathogenesis and therapy

Emerging concepts in the areas related to the pathogenesis and treatment of atopic dermatitis are reviewed. In particular, recent findings have revealed several key steps in the maintenance of a vicious circle of spongiotic dermatitis associated with elevated T-lymphocyte activation, hyperstimulatory Langerhans cells, defective cell-mediated immunity, and B-cell IgE overproduction. The discovery of specific IgE-binding structures on Langerhans cells provides a mechanism for Langerhans cells to capture and present IgE-targeted allergens to allergen-specific T cells. Furthermore, certain microbial allergens that tend to preferentially elicit IgE-type responses also elicit a T-cell response dominated by the IgE-inducing lymphokine interleukin 4. Repeated stimulation by activated Langerhans cells appears to induce just such a response. Abnormal biochemical responsiveness and mediator release by AD monocytes, mast cells, and eosinophils also participate in the sustainment or initiation of such a vicious circle, and contribute directly to the dermatitis as well. Developments in the areas of neuropeptides, genetics, microbial superantigens, and cytokine networks in the skin also appear to have promise in providing a rational link between immune defects and the inflammatory events in AD. Conventional therapy remains the mainstay of atopic dermatitis management; however, new therapies based upon the above concepts are being tested in clinical trials. Although the difficulty of objectively grading AD lesional activity and the high placebo response of AD patients hampers the interpretation of many reports, several types of approaches are coming into focus. The effectiveness of cyclosporin A, which targets T-cell activation and antigen presentation, indicates that additional agents with such activity should be effective, and verifies the criticality of these cells in AD pathogenesis. Therapy with biologic response modifiers, such as interferon gamma or thymopentin, is oriented toward normalization of imbalanced immune responsiveness, rather than direct suppression of the immune system. The mechanism of action of and toxicities of Chinese herbal mixtures require further investigation, but may reveal hitherto unconsidered avenues. Other recent therapeutic trials have focused on reduction of trigger factors, such as house dust mite exposure, foods, and the abnormal epidermal lipid barrier to irritation.

Atopic dermatitis--messengers, second messengers and cytokines

Atopic dermatitis (AD) shows many complex and interacting abnormalities of pharmacology, immunology and cellular control. Recent research in atopy has concentrated on abnormalities of cytokine production by T-helper cells. It is possible that cytokine imbalance causes many of the pharmacological and immunological changes seen in the disease. However, studies of second messenger control of cytokine release show that different second messenger signals may relate to the release and activation of particular cytokines. This review summarizes these findings and discusses how the second messenger defects reported in AD may relate to the abnormal cytokine profiles and the pharmacological abnormalities seen in the condition.

Subacute panencephalitis associated with chronic graft-versus-host disease

A unique form of subacute panencephalitis developed in a child with aplastic anemia 8 months after an allogeneic bone marrow transplantation (BMT). It was characterized by parenchymal infiltration of CD3 lymphocytes, a marked increase in the number of microglia strongly expressing HLA-DR antigens in both the gray and white matter, and diffuse degeneration of the cerebral white matter. The onset of neurological symptoms coincided with the development of chronic systemic graft-versus-host disease (GVHD). Cellular infiltrates in the CNS lesions were exclusively CD3 lymphocytes intermingled with a small number of monocytes labeled with CD68. There was a preponderance of cells of the CD45RB phenotype. The pathological changes in visceral organs were consistent with those of chronic GVHD. In addition, scrutiny of immunohistochemistry disclosed sparse infiltration of CD3 lymphocytes and diffuse gliosis in the cerebral white matter of another child with chronic GVHD who died 9 months after allogeneic BMT. These cases are suggestive of a potential risk of CNS involvement in GVHD.

Phenotypic determination of T-lymphocytes responding to chemotactic stimulation from fMLP, IL-8, human IL-10, and epidermal lymphocyte chemotactic factor

Human T lymphocytes were collected after they had migrated towards N-formyl-methionyl-leukylphenylalanine (fMLP), rIL-8, human IL-10 (hIL-10), and epidermal lymphocyte chemotactic factor (ELCF). They were stained for determination of their phenotype by FACS analysis using anti-CD4, -CD8, -CD18, -CD45R0 and OPD4 antibodies. Human IL-10 increased the percentage of CD8+ T lymphocytes in the migrating cell population by 152% compared with cells migrating towards the medium and decreased the number of CD4+ T lymphocytes by 79%. ELCF increased the number of CD4+ T lymphocytes by 18%, and the number of CD45R0+ T lymphocytes by 52%, while the number of CD8+ T lymphocytes was decreased by 20%. rIL-8 increased the number of CD4+ T lymphocytes and decreased the CD8+ T lymphocytes. The distribution of the different subpopulations of T lymphocytes was not changed significantly by fMLP. The observed changes in the phenotypes did not occur when incubating T lymphocytes with the chemotaxins. Our observations demonstrate that individual chemotactic factors will attract specific subsets of T lymphocytes. They may help to explain the predominance of memory T lymphocytes (CD4R0+, CD4+) in allergic contact dermatitis and certain other skin diseases. They also confirm the results of a recent study, that showed hIL-10 to be selectively chemotactic for CD8+ T lymphocytes.

Selective activation of circulating CD4+ lymphocytes in severe adult atopic dermatitis

An analysis of peripheral blood lymphocyte subsets and their expression of activation markers was performed using flow cytometry in 12 adult patients with severe atopic dermatitis, and compared with 14 normal individuals. Repeated measurements were made over an 8-week period during which disease activity was also assessed. Increased percentages of activated and unactivated CD4+ lymphocytes, and decreased percentages of CD8+ cells were observed in atopic dermatitis. Increasing disease activity was associated with an increase in the proportion of activated and unactivated CD4+ lymphocytes and a fall in the proportion of CD8+ cells. This study demonstrates that in adults with severe atopic dermatitis, increasing disease activity is associated with selective activation of CD4+ lymphocytes and a relative expansion of the CD4+ cell subset.

Functional characterization of skin-infiltrating lymphocytes in atopic dermatitis

Skin-infiltrating lymphocytes (SIL) were isolated from skin biopsies of patients with hyperimmunoglobulin E (IgE) atopic dermatitis (AD) and expanded in vitro in the presence of IL-2 in combination with IL-4. Phenotypic analysis of skin-derived cells revealed the predominance of CD4+ T helper/inducer phenotype in SIL populations. In 3H-thymidine incorporation assays, SIL showed proliferation in response to IL-2, IL-3, IL-4, ionomycin (Io) + 12-o-tetradecanoyl-phorbol-13-acetate (TPA) and OKT3 + TPA. OKT4 with and without TPA did not induce proliferation. Tumour necrosis factor alpha (TNF-alpha) did not block proliferative responses of SIL to IL-2 and IL-4. Cultured SIL showed no cytotoxic activity against K562 and Jurkat target cells. Expanded skin-derived T cells were tested for their capacity to secrete several cytokines in vitro. SIL secreted significant amounts of IL-4, GM-CSF and TNF-alpha upon stimulation with mitogens but failed to secrete IFN-gamma. Io in combination with phorbol-ester induced the secretion of larger amounts of IL-4, GM-CSF, TNF-alpha and low amounts of IFN-gamma. The data indicate that SIL derived from AD lesions were defective in their capacity to secrete IFN-gamma but were enriched in T cells capable of producing IL-4 upon stimulation. The results support the possibility of a predominant 'TH2-like' cell-mediated immune response in lesional skin of AD patients.

A comparison of expression of surface-bound immunoglobulin E on antigen-presenting cells in cutaneous tissue between patients with allergic, irritant and atopic dermatitis

The expression of surface-bound immunoglobulin E by dendritic cells within cutaneous tissue has been compared in atopic and contact dermatitis. 45 patients were recruited into 4 groups using clinical criteria and patch testing to a standard series of allergens: atopic (12 cases), allergic contact dermatitis (14 cases), irritant contact dermatitis (10 cases) and the control group (9 cases); using clinical criteria and patch testing to a standard series of allergens. Skin biopsies from each patient were analysed by the indirect immunofluorescence technique. This differentiated 3 patterns of cutaneous IgE distribution: (i) no detectable cutaneous IgE; (ii) detection of IgE solely within the dermis; (iii) detection of IgE within both epidermis and dermis. Detection of IgE within the epidermis was always associated with the presence of IgE within the dermis. In each case, IgE was surface-bound by dendritic cells. Immunoglobulin E was detected within both epidermis and dermis in skin biopsies from 8 (66.7%) atopic patients and 2 (20%) patients with irritant contact dermatitis. No other cases demonstrated IgE deposition within both the epidermis and dermis. Atopic patients were significantly more likely to have detectable IgE deposition, within both epidermis and dermis, than patients with contact dermatitis (allergic and irritant groups combined, p = 0.0011) or controls (p = 0.0049). This finding suggests that the demonstration of IgE within both epidermis and dermis supports a diagnosis of atopic dermatitis. It would therefore be of value in differentiating between atopic and contact dermatitis, where clinical diagnosis is in doubt.

Memory T cells represent the predominant lymphocyte subset in acute and chronic liver inflammation

T cells can be divided into two main phenotypic subpopulations-i.e., the CD45RA-positive (2H4-positive) "naive" subset and the CD45RO-positive (UCHL1-positive) "memory" subset. In light of this recent functional reinterpretation of T-lymphocyte subpopulations, we reinvestigated the composition of the inflammatory infiltrate in liver biopsy specimens from patients with acute and chronic hepatitis. In normal liver, the few scattered mononuclear cells present in portal tracts and in the intralobular parenchyma consisted of both CD45RA-positive (2H4-positive) naive and CD45RO-positive (UCHL1-positive) memory T cells. In inflammatory liver diseases, portal tract and periportal and intralobular areas of inflammation consisted virtually only of CD45RO-positive (UCHL1-positive) memory T cells, which strongly expressed the CDw29 (4B4) antigen, and the adhesion molecules LFA-1, CD2, LFA-3, CD44 and VLA-4 and the activation marker human leukocyte antigen-DR. These results indicate that activated memory T cells represent the predominant subpopulation of lymphocytes in areas of liver inflammation. Memory T cells strongly express various homing receptors and adhesion molecules, which probably allow them to accumulate at inflammatory sites and to strengthen interaction with target cells. Furthermore, the increased number of memory T cells with enhanced interferon-gamma production in areas of liver inflammation may contribute to the maintenance and up-regulation of immune responses occurring in inflammatory liver diseases.

Interleukin-4 promotes the expansion of skin-infiltrating lymphocytes from atopic dermatitis in vitro

Functional studies of lymphocytes in atopic dermatitis (AD) have so far focused on peripheral blood mononuclear cells (PBMC), whereas cells at the involved site, the skin, have not been examined. Accordingly, we have developed methods to generate lymphocyte cultures from biopsies of inflammatory skin areas. Skin-infiltrating lymphocytes (SIL) were isolated from skin biopsies of 6 patients with severe AD and expanded in vitro in the presence of interleukin-2 (IL-2) without additional antigens. After 6-10 d in culture, outgrowth of mononuclear cells from biopsy tissue was observed in all cases. Phenotypic analysis of skin-derived cells revealed the predominance of CD4+ T-helper/inducer phenotype in SIL populations. Parallel cultures of SIL and PBMC showed an increase and expansion of CD8+ T cells in cultured PBMC, whereas the CD4+ phenotype was predominant in SIL cultures. As indicated by their expression of HLA-DR and CD25 antigens, most of the SIL were activated and the cells mainly expressed T-cell receptors (TCR) composed of alpha and beta chains. Different strategies for expansion of SIL in vitro were examined. High levels of IL-4 (1,000 U/ml) in combination with IL-2 (50 U/ml or 1,000 U/ml) preferentially promoted growth of SIL derived from AD and were much more effective than IL-2 alone. No cells expanded in cultures with IL-4 alone. SIL grown with high concentrations of IL-4 contained a significant proportion of double-positive CD4+8+ cells. No other marked differences were observed in the distribution of T cell subsets in cultures propagated under different conditions for 21 d. Our results demonstrate the feasibility of growing infiltrating T lymphocytes from inflammatory skin of AD patients. The use of high concentrations of IL-2 in combination with high levels of IL-4 allows a large expansion of these cells and thus represents a useful strategy to expand cells for further functional and molecular biologic studies.

Contact urticaria due to the common stinging nettle (Urtica dioica)--histological, ultrastructural and pharmacological studies

A frequent cause of contact urticaria is skin exposure to the common stinging nettle (Urtica dioica). The urticaria is accompanied by a stinging sensation lasting longer than 12 h. Little is known of the cellular and molecular mechanism of stinging-nettle urticaria. After preliminary pharmacological analysis of pro-inflammatory activity in nettle stings, the cellular response of mononuclear cells, polymorphonuclear cells and mast cells was examined in six people 5 min and 12 h after nettle contact. Only mast cell numbers were significantly increased at 12 h. Ultrastructurally, some mast cells showed evidence of degranulation at 5 min and 12 h. At 12 h mast cells were closely associated with dermal dendritic cells and lymphocytes suggesting a functional unit. The mean histamine and serotonin contents of a nettle hair were found to be 6.1 ng and 33.25 pg, respectively. Nettle-sting extracts did not demonstrate histamine release from dispersed rat mast cells in vitro. These results suggest that part of the immediate reaction to nettle stings is due to histamine introduced by the nettle. However, the persistence of the stinging sensation might suggest the presence of substances in nettle fluid directly toxic to nerves or capable of secondary release of other mediators.

Flare factors and atopic dermatitis: the role of allergy

Atopic dermatitis is a genetically determined eczematous skin disease strongly influenced by environmental conditions called flare factors. Allergic reactions are one such flare factor. These reactions include contact urticaria, allergic contact dermatitis, and late phase reactions. Contact urticaria could induce eczema by eliciting scratching. A late phase reaction may be involved in eczema produced by prolonged epicutaneous applications of antigens in individuals with immediate sensitivity to these antigens. Mechanisms of allergic contact dermatitis might also elicit dermatitis. Environmental allergens may include mold, dust, mite, pollens, foods, danders and bacteria.

IgE-positive epidermal Langerhans cells in allergic contact dermatitis lesions provoked in patients with atopic dermatitis

To see whether or not IgE-bearing epidermal Langerhans cells are specific to skin lesions of atopic dermatitis (AD), we performed immunohistochemical and immunoelectron microscopic examinations of dinitro-chlorobenzene (DNCB) contact dermatitis lesions provoked in uninvolved skin of eight patients with AD. In all of the eight examined, IgE-positive epidermal Langerhans cells were observed in the DNCB dermatitis lesions. Typical staining of anti-IgE was absent in the epidermis of normal-appearing skin of five patients with AD. Thus, it is likely that IgE positive epidermal Langerhans cells non-specifically occur in different eczematous diseases provoked in patients with AD.

Occurrence of IgE-bearing epidermal Langerhans cells in atopic eczema: a study of the time course of the lesions and with regard to the IgE serum level

Uninvolved and lesional skin of untreated and treated patients with atopic eczema has been investigated immunohistochemically to determine the conditions in which IgE-bearing CD1a+ Langerhans cells/indeterminate cells (LC/IC) occur in this disease. IgE-bearing epidermal dendritic cells were present in patients with elevated IgE serum level (greater than 300 UI/ml) and the staining pattern was stronger in lesional skin. On double immunostaining, a subpopulation of CD1a+ LC/IC was found not to bear IgE molecules as determined by the ratio IgE+/CD1a+ cells on serial sections as well. The ratio IgE+/CD1a+ cells decreased in patients who underwent a local therapy with glucocorticosteroids. These results suggest that the expression of IgE receptors and/or binding of IgE molecules on epidermal LC/IC in atopic eczema may be controlled by a complex network of mediators from the epidermis or the inflammatory infiltrate, or both, and that this phenomenon could be down regulated by glucocorticosteroids.

The preferential accumulation of helper-inducer T lymphocytes in inflammatory lesions: evidence for regulation by selective endothelial and homotypic adhesion

The mechanisms which lead to the accumulation of T lymphocytes into inflammatory lesions are not clearly understood. We have previously shown that synovial CD4 T lymphocytes are mostly CDw29+UCHL1+ (helper-inducer cells) and very few carry the CD45R antigen which identifies the suppressor-inducer subset. Synovial CD8+ cells are also CDw29+UCHL1+CD45R-. In the present study, lymphocytes from pleural and peritoneal inflammatory infiltrates were shown to have a similar phenotypic pattern. Furthermore, it was demonstrated that the CDw29+UCHL1+ subset had a greater ability than CD45R+ cells to adhere to endothelial cells and to form homotypic clusters. Differential surface expression of LFA-1 on the two subsets was also shown, but this could not account for the demonstrated adhesion differences. Differences in adhesion between CDw29+/UCHL1+ and CD45R+ cells may explain the preferential accumulation of CDw29+/UCHL1+ cells in inflammatory infiltrates and underlie some of the functional differences between cells taken from sites of chronic inflammation and those from peripheral blood.