Severe atopic dermatitis is associated with a reduced frequency of IL‐10 producing allergen‐specific CD4+ T cells

Summary Background.  Several studies have investigated levels of T‐cell‐derived interleukin (IL)‐10 in individuals with atopic dermatitis, with conflicting results. Aims/Hypothesis.  In order to address whether stratification of disease severity may help resolve the different findings, the hypothesis was tested that individuals with severe atopic dermatitis have a lower frequency of circulating IL‐10‐producing, allergen‐specific CD4+ T cells than do individuals with mild disease. Methods.  Using peripheral blood mononuclear cells derived from individuals with severe (n = 12) and mild atopic dermatitis (n = 10) and from nonatopic controls (n = 10), we investigated production by CD4+ T cells of tumour necrosis factor (TNF)‐α, IL‐4, IL‐5, IL‐13 and IL‐10 in response to phorbol myristate acetate/ionomycin and Der p1 allergen. Results.  It was observed that there were significantly higher frequencies of allergen‐specific circulating CD4+ T cells producing TNF‐α‐ IL‐4‐, IL‐5‐ and IL‐13, and lower frequencies of these cells producing IL‐10 in individuals with severe atopic dermatitis compared with mildly affected individuals and nonatopic controls ( P  < 0.01 for all comparisons). Furthermore, the Der p1‐specific CD4+ T cells were enriched within the subset of cells positive for cutaneous lymphocyte‐associated antigen. Conclusions.  Analysis of levels of allergen‐specific CD4+ T‐cell production of IL‐10 in relation to disease severity argues in favour of a role for IL‐10 in the control of atopic dermatitis.