High frequency of IL-4-producing CD4+ allergen-specific T lymphocytes in atopic dermatitis lesional skin.

In atopic dermatitis (AD) hypersensitivity reactions to allergens are commonly observed and are assumed to make a major contribution in the pathomechanism of the disease. It may be expected that allergen-reactive Th cells play a central role in these reactions. In the present study the occurrence and function of allergen-specific T lymphocytes in dermal inflammatory lesions were studied. To this aim panels of randomly cloned CD4+ T cells from lesional skin biopsies of two housedust mite Dermatophagoides pteronyssinus (Dp)-allergic AD patients were screened for reactivity with Dp allergens. The results were compared with similar tests for Dp reactivity of T-lymphocyte clones (TLC) from the peripheral blood of these patients. In the panels of TLC generated from lesional skin (S-TLC), a considerable number of TLC appeared to be Dp-specific, 47% (n = 17) and 10% (n = 29), respectively. In the panels from the peripheral blood, the percentages of Dp-specific TLC were only 0% (n = 22) and 3% (n = 34), suggesting accumulation or expansion of these T cells in lesional skin. The function of these TLC was studied by assaying the secretion of IL-4 and IFN-gamma, which have been shown to be produced in aberrant ratios by Dp-specific TLC from the peripheral blood of AD patients (Wierenga et al: J Immunol 144:4651, 1990). All Dp-specific S-TLC produced IL-4 in combination with no or low levels of IFN-gamma, whereas many of the non-Dp-specific S-TLC and blood-derived TLC (B-TLC) were observed to produce high levels of IFN-gamma without significant amounts of IL-4. A functional consequence of these cytokine profiles was demonstrated by the finding that TLC producing substantial amounts of IL-4 enhanced expression of the low-affinity Fc receptor for IgE (CD23) on antigen-presenting cells to a greater extent than did IFN-gamma-producing TLC.