Mast cell number and phenotype in chronic idiopathic urticaria,☆☆,

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Abstract

Background: Increased levels of histamine have been previously demonstrated in patients with chronic idiopathic urticaria. Objective: The purpose of the study was to determine whether increased numbers of mast cells are present in lesional skin from such patients. Methods: Mast cells have been quantified in lesional (n = 11) and nonlesional (n = 9) skin from patients with chronic idiopathic urticaria and compared with site-matched skin from healthy control subjects (n = 10). Mast cells were identified by using a sensitive, double-labeling immunohistochemical technique with specific monoclonal antibodies to mast cell tryptase and chymase and quantified under light microscopy. Results: No significant differences in mast cell numbers from lesional, nonlesional, or control skin were observed (p > 0.1, Student's t test). In both patients with urticaria and control subjects, more than 99% of cutaneous mast cells contained tryptase and chymase. Conclusions: These data indicate that increased skin histamine in chronic idiopathic urticaria is not caused by increased mast cells and may alternatively reflect an increase in histamine content per mast cell, enhanced mast cell activation, or recruitment of basophils into skin in patients with chronic idiopathic urticaria. (J ALLERGY CLIN IMMUNOL 1995;96:360-4.)

Section snippets

Subjects

Eleven patients with chronic idiopathic urticaria were recruited (6 men and 5 women; age range, 21 to 63 years), and nine consented to skin biopsies of both lesional and nonlesional skin. Chronic idiopathic urticaria was defined as the appearance of recurrent, multiple cutaneous wheals for more than 3 months, occurring at intervals of not less than 1 week. All patients were subject to a detailed history, physical examination, and as appropriate, laboratory investigation to exclude underlying

RESULTS

No significant differences were observed among lesional, nonlesional, or control skin at either 0 to 183 μm or 183 to 366 μm from the dermo-epidermal junction (Table I, Fig. 1). With the exception of samples from two patients with urticaria (in which 95% and 96% of mast cells, respectively, were of the MCTC type in nonlesional skin), in other samples (from both patients with urticaria and control subjects) more than 99% of mast cells present were of the MCTC type.

. Scatter plot showing paired

DISCUSSION

Chymase and tryptase are located almost exclusively in mast cells, basophils containing negligible amounts of tryptase (0.04 pg/cell) and undetectable amounts of chymase. The alkaline phosphatase–conjugated G3 antibody stains only mast cells.11 Similarly, eosinophils, neutrophils, monocytes, and lymphocytes have no detectable tryptase.12, 13 Thus immunohistochemical localization of these two enzymes provides a discriminating marker for human mast cells. Although chymase and tryptase are

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  • Cited by (0)

    From the Department of Allergy & Respiratory Medicine, United Medical & Dental Schools, Guy’s Hospital, London.

    ☆☆

    Reprint requests: H. Lee, Department of Allergy & Respiratory Medicine, United Medical & Dental Schools, Guy's Hospital, St. Thomas' St., London SE1 9RT, England.

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