Interleukin-4-positive mast cells are highly associated with the extent ofimmediate allergic wheal reaction in the skin

Background: In addition to histamine, mast cells contain other potent media tors which can contribute to the allergic wheal reaction in the skin. Methods: To study the association of tryptase-, chymase-, and interleukin-4 (IL-4)-positive mast cells with the size of the prick-test wheal reaction, 50 sensitive atopic subjects were prick-tested with the cow-dander allerge n on the forearm skin, and the wheal area was measured. A corresponding sit e of intact healthy-looking skin was biopsied and examined enzyme-histochem ically for tryptase and chymase. A double-staining method was used to demon strate the immunoreactivity of IL-4 and chymase inhibitors (alpha (1)-prote inase inhibitor and alpha (1)-antichymotrypsin) in mast cells. The levels o f total and cow-specific immunoglobulin E (IgE) were measured in serum. Results: The number of tryptase- and chymase-positive mast cells or those c ontaining chymase inhibitors revealed no correlation with the wheal reactio n. In contrast, both the percentage and the number of IL-4-positive mast ce lls showed significant positive correlation with the wheal size per se (P < 0.0001), as well as with the ratio of the wheal size by cow allergen to th at by histamine control (P < 0.003). In addition. tryptase-, chymase-, and IL-3-positive mast cells correlated with total IgE, but not with specific I gE, levels, and they showed no relation to the clinical manifestation of at opic disease, asthma or atopic dermatitis. Conclusions: The novel finding was that IL-4-positive, but not tryptase- an d chymase-positive, mast cells are intimately associated with the extent of the prick-test wheal.