CD4+ cells proliferate after peanut‐extract‐specific and CD8+ cells proliferate after polyclonal stimulation of PBMC of children with atopic dermatitis

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Abstract
Few studies describe in vitro food-allergen induced proliferative responses and cytokine production of PBMC of children with atopic dermatitis. This is especially true for peanut-allergen. To analyse the specificity of the T cell in proliferative responses, in children with atopic dermatitis with or without peanut allergy and healthy age-matched children. Proliferative responses were measured by [3H]-thymidine incorporation and by expression of the intracellular Ki67-antigen using flow cytometry after antigen-specific stimulation of PBMC with peanut-extract (day 7) or polyclonal stimulation with Phorbol-12myristate-13acetate and Ca-ionophore (day 3). Cytokine mRNA (Interferon-gamma (IFNγ), IL-4) was detected by semiquantitative RT-PCR. Cytokine production (IL-4, IFNγ) was measured by ELISA. Peanut-extract induced proliferative responses of PBMC from children with atopic dermatitis and peanut allergy (AD+PA+) were significantly higher as compared with the other groups studied. Ki67-antigen double staining revealed that 80–100% of the proliferating cells were CD4+. These proliferative responses correlated significantly with the increase in IL-4 mRNA expression after peanut-extract specific stimulation. After polyclonal stimulation, however, CD8+ cells preferentially proliferated. The degree of proliferation after polyclonal stimulation correlated inversely with the ratio of IL-4/IFNγ production. The principal responding population of T cells in proliferative responses is different after peanut-extract specific and polyclonal stimulation of PBMC from AD+PA+ patients. Furthermore, we found indirect evidence that the PBMC fraction of AD+PA+ children contains increased frequencies of peanut-specific T helper-2 cells.