Role of mast cells in allergic inflammation in the skin

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Mast cells were raised from umbilical cord blood cells in the presence of stem cell factor and interleukin 6. Immunocytochemical staining for mast cell proteases revealed that all cells contained tryptase. Anti-IgE effectively stimulated the mast cells to release histamine in a dose-dependent, time-dependent manner. Calcium ionophore A23187 also induced histamine release in a dose-dependent, time-dependent manner. Compund 48/80 and substance P failed to induce histamine release from the cells. As a next step of the study, the effects of ultraviolet light irradiation on substance P-induced histamine release from rat peritoneal mast cells were investigated. Ultraviolet light B (UVB) irradiation inhibited the histamine release in a dose-dependent manner, and 8-methoxypsoralen plus long-wave ultraviolet light (UVA) irradiation inhibited in a dose-dependent manner of UVA.UVB irradiation and 8-methoxypsoralen plus UVA irradiation inhibited the histamine release through the suppression of intracellular calcium concentrations.Mast cell subtype of patients with mastocytosis was investigated. Mast cells containing tryptase and chymase were the only type seen in the skin lesions of a patient with urticaria pigmentosa. Mast cells containing tryptase and chymase were predominant in the nonlesional skin of a patient with indolent systemic mastocytosis, however mast cells containingtryptase (but not chymase) were predominant in the lesional skin of the patient. Biopsy specimens from not only the skin but also the lymphnode, bone marrow, bronchus, nasal mucosa, gastric mucosa showed infiltrations of mast cells containing tryptase (but not chymase) in a patient with systemic mastocytosis. Blood levels of histamine, tryptase, leukotriene C4 and urine levels of methylhistamine, leukotriene E4 were elevated in the patients with mastocytosis.