Expansion and Proliferation of Skin-Homing T Cells in Atopic Dermatitis as Assessed at the Single Cell Level

Abstract

Background: Sensitization to aeroallergens is a frequent event in patients with atopic dermatitis (AD). The role of allergen-specific T cells in the pathogenesis of AD is, however, not fully clear. A detailed immunological characterization of allergen-specific T cells able to migrate to inflamed skin might therefore be helpful in determining the relevance of allergen-specific T cells to clinical symptoms. Objective: To establish a simple assay to simultaneously monitor the expression of skin-related homing molecules and their proliferative response to an allergen on peripheral T cells. To evaluate whether this assay is able to identify AD patients in whom exposure to an allergen induces dermatitis. Methods: The expression of CLA, CD7 and CD4 was simultaneously measured by flow cytometry with the DNA content as a parameter of proliferation at the single cell level. House dust mite antigen (DerP) and tetanus toxoid (TT) were used as antigens. Results: CD4+ CLA+ CD7–, but not CLA– T cells from patients with AD proliferated and expanded following DerP stimulation. In contrast, TT stimulation resulted in proliferation of both, CLA+ and CLA– T cells from both, atopic and healthy donors. Conclusions: Single cell analysis revealed a predominant localization of allergen-reactive T cells within the CD7– CLA+ CD4+ T cell subset in AD. Thus, this simple assay not only confirms previously published results, but also extends our knowledge on the biology of CLA and CD7 cells in AD. Ultimately, this will be helpful in classifying those patients who might benefit from allergen avoidance therapies.

Early pediatric atopic dermatitis shows only a cutaneous lymphocyte antigen (CLA)+ TH2/TH1 cell imbalance, whereas adults acquire CLA+ TH22/TC22 cell subsets

“…8, 9–11 Most T-cells in AD lesions are CD45RO + memory cells that express the skin-homing receptor cutaneous lymphocyte antigen (CLA). 12–14 Circulating CLA + T-cells are expanded in AD, respond to skin-associated allergens, and play a role in disease pathogenesis. 14–17 CLA + T-cells have been also demonstrated to be peripheral biomarkers in several inflammatory skin diseases.…”

“…12–14 Circulating CLA + T-cells are expanded in AD, respond to skin-associated allergens, and play a role in disease pathogenesis. 14–17 CLA + T-cells have been also demonstrated to be peripheral biomarkers in several inflammatory skin diseases. 18 The need for large biopsies to classify T-cell subsets limits the feasibility of intracellular cytokine staining (ICS) of skin from adults and even more so in children.…”

Circulating CLA+T cells in atopic dermatitis and their possible role as peripheral biomarkers

“…Most T cells in AD skin lesions are CLA + CD45RO + memory cells . Circulating CLA + T cells are expanded in AD, respond to skin‐associated allergens, infiltrate skin lesions, and are central players in the initiation and perpetuation of AD lesions . Additionally, it has been shown that bacterial toxins increase CLA expression in superantigen‐mediated diseases and that AD severity is correlated with CLA + T‐cell‐attracting chemokines in serum .…”

T Cell Epitope-Specific Defects in the Immune Response to Cat Allergen in Patients with Atopic Dermatitis

“…Allergen-reactive T cells derived from patients with AD are predominantly CD4 þ T cells which express the skinhoming marker, cutaneous lymphocyte-associated antigen (CLA), suggesting a direct function of these cells in the disease (Santamaria Babi et al, 1995;Jung et al, 2003). Despite this, few studies of AD patients have examined T cell responses in allergen-specific systems.…”