Ilse C. Bihari

Biphasic response against aeroallergen in atopic dermatitis showing a switch from an initial TH2 response to a TH1 response in situ: An immunocytochemical study

In the pathogenesis of atopic dermatitis (AD), IgE plays an important role; and TH2 cells, producing IL-4, have been ascribed a key role in allergic diseases such as AD. To investigate the role of TH subpopulations in the onset and continuation of AD, we performed atopy patch tests (APTs) with house dust mite allergen in patients with AD. Punch biopsy specimens were taken from the APT site, and sections were immunocytochemically double-stained for IL-4 and interferon-gamma together with different membrane markers. This provides a unique model for studying the kinetics of the TH0, TH1, and TH2 responses in situ. The results show that in lesional skin interferon-gamma-positive cells predominate over IL-4-positive cells. The interferon-gamma-positive cells are mainly CD3+ and, in particular, CD4+ cells; the remainder are CD8+, RFD-1+, and RFD-7+ cells. The IL-4-positive cells are exclusively CD4+ T cells; no eosinophils or mast cells were found to stain for IL-4. With regard to the TH cell response, a clear dichotomy of the eczematous response to allergen in skin was observed. In the initiation phase IL-4 production by TH2 and TH0 cells is predominant over interferon-gamma production by TH1 and TH0 cells. In the late and chronic phases the situation is reversed and interferon-gamma production by TH1 and TH0 cells predominates over IL-4 production by TH2 and TH0 cells. Understanding the relationship between the observed biphasic response and clinical manifestation of AD is important for the development of therapeutic strategies.

Adhesion molecule expression on skin endothelia in atopic dermatitis: Effects of TNF-α and IL-4

Abstract Background: Atopic dermatitis (AD) is characterized by skin infiltrates of leukocytes, such as lymphocytes and eosinophils. Objective: To describe the mechanisms determining this inflammatory process, we have analyzed expression of adhesion molecules and their regulation on skin endothelial cells (ECs). Methods: Expression of adhesion molecules on ECs was analyzed by immunohistochemistry by using Ulex europaeus agglutin 1 as a pan-endothelial marker. Results: Vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and P-selectin were not found in skin of nonatopic individuals, whereas expression of these surface molecules was observed in nonlesional skin of patients with AD and was even more pronounced in lesional skin or after epicutaneous application of aeroallergen. Induction of adhesion molecule expression was examined on both macrovascular ECs from human umbilical cord vein (HUVECs) and human microvascular ECs (HMEC-1) from skin. TNF-α very potently upregulated adhesion molecule expression in vitro on both EC cell types. To verify the in vivo relevance of TNF-α, we performed TNF-α staining in the skin. TNF-α was observed in the dermis of nonatopic skin, both in chymase-containing mast cells and CD68 + macrophages. The increase in the number of TNF-α–containing cells was concomitant with the increase in adhesion molecule expression in the skin of patients with AD. IL-4 is supposed to be important in atopic diseases because of its IgE- and VCAM-1–inducing properties. However, IL-4 addition failed to induce VCAM-1 expression on HMEC-1, although in the same set of experiments, a clear induction of VCAM-1 expression by IL-4 on HUVECs was demonstrated. Flow cytometry revealed the absence of IL-4 receptor α-chains on HMEC-1 and their presence on HUVECs. Immunohistochemistry examination on skin sections showed no binding of the IL-4R α-chain antibodies to ECs. Conclusion: We conclude that adhesion molecule expression is increased in the skin of patients with AD. Most probably, this increased expression is not a (direct) effect of IL-4 on skin endothelium, but other cytokines, such as TNF-α, might be responsible for this increased adhesion molecule expression. Continuous adhesion molecule expression may facilitate T-cell extravasation in a nonantigen–specific manner, thus explaining the presence of increased T-cell numbers in nonlesional skin of patients with AD. (J Allergy Clin Immunol 1998;102:461-8.)

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

Abstract 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

Nonspecific T-cell homing during inflammation in atopic dermatitis: Expression of cutaneous lymphocyte-associated antigen and integrin αEβ7 on skin-infiltrating T cells

Atopic dermatitis (AD) is a chronic skin disorder, characterized by infiltration of activated memory CD4+ T cells into skin. A model to study the onset of allergic inflammation in a patient with AD is the atopy patch test (APT), in which, by epicutaneous application of aeroallergen, an eczematous reaction is induced in 50% of sensitized patients with AD. Extravasation of T cells into skin is thought to be critically dependent on expression of the surface molecule cutaneous lymphocyte-associated antigen (CLA), which recognizes and binds its ligand E-selectin on endothelium. We studied the dynamics of expression of CLA and the gut homing receptor alphaE beta7 (HML-1) on T cells in the skin of patients with AD and in APT reactions and nickel and sodium lauryl sulfate patch test reactions by means of immunohistochemical double staining of skin biopsy specimens. The results show an increase in the number of CD3+ T cells in the lesional skin of patients with AD, APT reactions, and nickel and sodium lauryl sulfate patch test reactions as compared with nonlesional skin of the same patients and nonatopic individuals. In contrast, the percentages of CLA+ T cells in the lesional skin of patients with AD, in the APT reactions, and in sodium lauryl sulfate and nickel patch test reactions were decreased. In addition, we found a marked expression of alphaE beta7 by T cells present in skin, indicating a nonspecific influx of T cells during allergic skin inflammation. We propose that during allergic skin inflammation CLA expression is not a prerequisite for cutaneous T-cell infiltration. CLA expression may be important for T cells to extravasate from blood into skin during immune surveillance or for retention of allergen-specific T cells in skin.

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.

Expression of VCAM‐1, ICAM‐1, E‐selectin, and P‐selectin on endothelium in situ in patients with erythroderma, mycosis fungoides and atopic dermatitis

Background: Erythroderma may result from different causes. At present it is unclear whether the patho‐mechanisms that lead to these different types of erythroderma are identical or different. Adhesion molecules and their ligands play a major role in endothelial‐leukocyte interactions, which affect the binding, transmigration and infiltration of lymphocytes and mononuclear cells during inflammation, injury, or immunological stimulation. The aim of this study was to investigate the adhesion molecule expression on endothelial cells in erythroderma in situ.

Interleukin 4 and interferon-γ expression of the dermal infiltrate in patients with erythroderma and mycosis fungoides. An immuno-histochemical study

Background: Erythroderma, or generalized erythema of the skin, may result from different causes. At present it is unclear whether the underlying patho‐mechanisms that lead to erythroderma are identical or different depending on the original disease. The aim of this study was to investigate the dermal cytokine profile in different types of erythroderma and mycosis fungoides.

Pruritus and mast cell proliferation in the skin of haemodialysis patients

Uremic pruritus is one of the most disturbing symptoms in patients with end-stage renal failure, affecting 60% to 65% of haemodialysis patients [1, 2]. Although several theories have been suggested, the etiopathogenesis of uremic pruritus remains unclear. Because dermal mast cells are regarded as one of the main sources of histamine and elevated levels of plasma histamine are found in uremic patients [2], this study was undertaken to evaluate mast cell proliferation in the skin of patients undergoing maintenance haemodialysis.