To determine whether mast cells in atopic dermatitis lesions express interleukin-4 and serve as the initial cytokine source required for Th2-cell differentiation.
Examined skin sections from 20 patients with atopic dermatitis, 10 patients with nummular eczema, and 5 healthy controls.
Performed sequential enzyme-histochemical staining for tryptase followed by polyclonal antibody immunostaining to quantify interleukin-4-positive mast cells in the upper dermis.
Interleukin-4-positive mast cell frequency in the upper dermis was significantly higher in lesional versus non-lesional atopic dermatitis skin (66±18% vs. 37±18%, P<0.0001), compared with nummular eczema (46±19% vs. 31±22%) and healthy controls (23±25%).
Lesional atopic dermatitis skin showed significantly higher mast cell interleukin-4 positivity than lesional nummular eczema (P<0.008), with mast cells serving as the primary interleukin-4 source in 40% of lesional and 100% of non-lesional atopic dermatitis specimens.