Tryptase-chymase double-positive human mast cells express the eotaxin receptor CCR3 and are attracted by CCR3-binding chemokines

Eosinophils, basophils, and Th2 cells express the chemokine receptor CCR3, which binds eotaxin, RANTES, and some other chemokines, Using immunohistoch emistry and how cytometry, we demonstrate that CCR3 is also expressed by a variable proportion of human mast cells in gut, skin, and lung tissue. By c ontrast, with the same anti-CCR3 antibody (B711), CCR3 was poorly if at all detectable on human Th2 cells in vitro and in vivo. Eotaxin neither induce d histamine release from purified human mast cells nor increased anti-IgE-s timulated histamine secretion. However, both eotaxin and RANTES elicited ma st cell migration in vitro with a similar efficacy. High percentages of CCR 3-expressing mast cells were present in the skin and in the intestinal subm ucosa; much lower percentages were found in the intestinal mucosa and in lu ng interstitium, Double immunostaining with anti-CCR3 and anti-chymase anti body showed that the vast majority of CCR3-expressing mast cells in the var ious tissues examined were tryptase-chymase double-positive. Therefore, try ptase-chymase double-positive mast cells express CCR3 and. are attracted by CCR3-binding chemokines, eotaxin, and RANTES, Our findings indicate that t hese chemokines may play an important role in the differentiation and/or mi gration of this mast cell subset in connective tissues, as well as in. site s of allergic inflammation.