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

Background 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. Objectives 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. Methods 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 (IFN), IL-4) was detected by semiquantitative RT-PCR. Cytokine production (IL-4, IFN) was measured by ELISA. Results 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 80100 percent 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/IFN production. Conclusions 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.