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

Immunoglobulin e-mediated allergy plays a role in atopic eczema as shown in the atopy patch test

Although the pathophysiology of immunoglobulin E (IgE)-mediated allergic rhinoconjunctivitis and bronchial asthma is rather well established, the role of allergy in atopic eczema (AE) is still controversial. By a technique called atopy patch test, aeroallergens like house dust mite, animal dander, or pollen were proven as relevant trigger factors in a subgroup of patients with AE. The atopy patch test is an epicutaneous patch test with such allergens known to elicit IgE-mediated reactions, and used for the evaluation of eczematous skin reactions. In a series of single-center and multicenter studies, a method was developed, standardized, and compared with other diagnostic techniques (radioallergosorbent test, skin prick test) in AE patients. With regard to clinical history, the most specific results were obtained with the atopy patch test (allergen-dependent, 69%-92%), whereas sensitivity was higher for skin prick test (range, 69%-82%) and specific IgE (range, 65%-94%). The characterization of a patient subgroup with relevant IgE-mediated allergy may lead to more efficient avoidance and eventually even specific immunotherapy strategies in the management of AE.

[Atopic patch test. Atopic eczema and allergy]

The role of IgE-mediated allergic reactions in atopic eczema remains controversial. Using the atopy patch test, aeroallergens such as house dust mites, animal dander or pollen can be identified as relevant trigger factors in a subgroup of patients with atopic eczema. The atopy patch test is an epicutaneous patch test employing allergens known to elicit IgE-mediated reactions and used to evaluate eczematous skin reactions. In a series of single- and multicenter studies, a method was developed, standardized and compared to other diagnostic techniques (specific serum-IgE, skin prick test) in atopic eczema patients. With regard to clinical history, the most specific results were obtained with the atopy patch test (allergen-dependent 69-92%), while sensitivity was higher for skin prick test (69-82%) and specific IgE (65-94%). The characterization of a patient subgroup with relevant IgE-mediated allergy may lead to more efficient avoidance and perhaps even specific immunotherapy strategies in the management of atopic eczema.

Longitudinal case analysis in atopic dermatitis

The current knowledge on atopic dermatitis comes mainly from cross-sectional studies, which are not suited to establish time-courses or causal links in complex diseases. As an alternative approach, the method of longitudinal case analysis by the autoregressive integrated moving average (ARIMA) method has been introduced to investigate the pathogenesis of atopic dermatitis. The method was applied to the investigation of 2 patients suffering from severe and moderate atopic dermatitis. Disease activity, peripheral blood parameters (differential blood count, lymphocyte subpopulations, immunoglobulin E, eosinophilic cationic protein, soluble interleukin-2 receptor), mental stress and environmental factors were determined daily for 50 days. Both patients showed a positive correlation between CD4+ and CD25+ T-cells, a negative correlation between CD16/56+ natural killer cells and CD4+ T-cells, a negative correlation between eosinophils and polymorphonuclear leukocytes, and a time-shifted positive correlation of up to 2 days between scores quantifying mental stress and disease activity. A positive correlation between T-cells and polymorphonuclear leukocytes, CD4+ T-cells and the CD45RA+ subtype, as well as a negative correlation between stress and eosinophils, sports and eosinophils, and sports and disease activity were found only in one patient with more severe atopic dermatitis. In conclusion, longitudinal time-series analysis might represent an interesting and adequate method to generate and test new hypotheses on biomedical problems which cannot be addressed by cross-sectional studies.

Comparative study of two cytofluorometric methods of analysis

Cytofluorometry of lymphocytes is an important technique in experimental biology and clinical medicine. One source of variability in the results with this technique stems from the difficulty of delineating cell subpopulations on a visual basis. We have evaluated the performance of a novel software method (Attractor), which introduces cluster analysis for the more precise definition of cell populations. Using 115 blood samples from patients with various immunological diseases, we compared the results obtained for 19 lymphocyte cell populations employing either the Attractor program or a conventional program (Cellquest). The analysis focused on inter-observer and inter-method variability and comparability. Inter-observer variability was significantly lower with the Attractor software, particularly when quantifying small cell populations such as activated subsets. The results obtained with both methods showed high correlation coefficients except for some cell populations that were either very small or which had to be calculated from the sum of other counts. The performance of the novel flow cytometric software is similar to software programs currently in use, but it offers an advantage for the definition of small and/or activated lymphocyte subpopulations. Moreover, the consistency of the measurements is better. A major disadvantage for statistical analysis, however, is that the Attractor program has not been adapted for non-parametric data.

Long-term application of extracorporeal photochemotherapy in severe atopic dermatitis

BACKGROUND

Extracorporeal photochemotherapy (ECP) using UVA irradiation of enriched leukocytes in the presence of methoxsalen as a photoactivatable substrate has been employed for the treatment of several immunologically mediated disorders.

OBJECTIVE

Our purpose was to determine the efficacy and safety of long-term ECP in the treatment of severe atopic dermatitis.

METHODS

Fourteen patients with severe recalcitrant atopic dermatitis were treated with ECP in an open clinical trial at 2-week intervals. Disease activity was scored before each ECP cycle by means of a standardized protocol.

RESULTS

A complete clinical remission was achieved in 4 patients (29%). Five patients (36%) experienced a substantial response with reduction of skin inflammation by at least 75%, whereas in one patient (7%) disease activity was reduced by more than 50%. Four patients were withdrawn from the study for unresponsiveness. No clinical signs of immunosuppression or other severe adverse events became evident.

CONCLUSION

Long-term ECP may have significant beneficial effects on the course of atopic dermatitis and should therefore be considered as a treatment modality for patients suffering from severe and otherwise refractory atopic skin disease.

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.

Enhanced expression of T-cell activation and natural killer cell antigens indicates systemic anti-tumor response in early primary cutaneous T-cell lymphoma

Indolent, primary cutaneous T-cell lymphomas (CTCL) are characterized by hyper-proliferation of malignant T-helper cells in the skin with a favorable prognosis in the early stages. Cytotoxic T cells (CTLs) are believed to be of major importance for tumor surveillance, but there is not yet sufficient evidence for a systemic anti-tumor response in mycosis fungoides (MF). On the contrary, there are hints of systemic immunodepression. We wondered whether signs of a systemic anti-tumor response were demonstrable in peripheral blood of patients with MF and CD30+ pleomorphic T cell lymphoma. Using multiparameter flow cytometry, we investigated blood samples from 39 CTCL patients at different stages and compared them with those from patients with psoriasis, atopic dermatitis, and healthy volunteers. In CTCL patients, an elevated number of lymphocytes expressing natural killer cell markers were found, as well as considerable T-cell activation, indicated by increased percentages of T cells expressing HLA-DR, IL-2 receptor alpha-chain, and transferrin receptor. The CD8+ T cells, which were the most strongly activated T-cell subset, were of polyclonal origin, as shown by their usage of different T-cell receptor families. The enhanced expression of activation antigens was associated with an increased proportion of CD8+ T cells with high expression of the adhesion molecule LFA-1, demonstrating the capacity for migration of these cells. These CD8+ effector cells are suspected to be CTLs and may be responsible for the favorable prognosis of indolent, primary CTCL. Interestingly, a stage-dependent decrease in T-cell activation antigen expression was observed, suggesting the development of a lack in tumor surveillance in advanced MF stages. Further investigations are necessary to verify whether any of the parameters determined are of predictive value for prognosis and response to therapy in CTCL.

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.

Monocyte phosphodiesterase abnormalities and dysregulation of lymphocyte function in atopic dermatitis

The immunologic aberrations associated with atopic dermatitis include the paradox of reduced cell-mediated immune responses in the setting of increased cell-mediated immunity features that resemble allergic contact dermatitis. In this review, we present evidence that abnormalities in monocytes and Langerhans cells alter the function of T-helper-cell subpopulations to cause the immunologic defects associated with atopic dermatitis. Increased monocyte prostaglandin E2 production inhibits Th1 responses, accentuating interleukin (IL)-4 secretion by Th2 cells. Elevated prostaglandin E2 secretion correlates with abnormally increased cyclic adenosine monophosphate-phosphodiesterase activity in monocytes and this, along with other defective inflammatory cell responses, can be normalized in vitro by phosphodiesterase inhibitors. It appears that in addition to prostaglandin E2, IL-10 acts to regulate the balance between Th1 and Th2 functional responses accounting for many atopic features, including increased IL-4, IL-5, and IL-6 production by T cells; increased IgE synthesis; decreased interferon-gamma production; and impaired cell-mediated immune responses. All of these abnormalities can be related to increased phosphodiesterase activity in atopic monocytes, and inhibition of this key enzyme appears to reverse atopic dermatitis inflammatory abnormalities in vitro and in vivo.

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.

Enhanced procoagulant activity of mononuclear leukocytes in patients with atopic dermatitis and psoriasis

Fibrin deposition is an important histopathological feature of inflammatory skin lesions and is mediated in part, by procoagulants generated by mononuclear leucocytes (MNL). We examined whether MNL from patients with atopic dermatitis or psoriasis generate enhanced procoagulant activity (PCA). MNL isolated from the peripheral blood of 15 healthy control individuals, 15 patients with atopic dermatitis and 15 patients with psoriasis were incubated for 24 h in the presence or absence of bacterial lipopolysaccharide (LPS). MNL or the cell culture supernatants were then added to recalcified human plasma to determine the clotting time. We found that in both atopic dermatitis and psoriasis MNL cultured in the presence or absence of LPS expressed greatly enhanced PCA (p < 0.01 to < 0.002). Supernatants from MNL cultures from patients with psoriasis, but not those from patients with atopic dermatitis, also generated augmented PCA (p < 0.002). In psoriasis, PCA normalized after successful topical treatment with anthralin. We conclude that enhanced PCA is a characteristic feature of MNL in both atopic dermatitis and psoriasis. In psoriasis the enhanced PCA is directly related to disease activity.