Human mast cell progenitors in peripheral blood from atopic subjects with high IgE levels.

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Abstract
Background It remains unclear whether the number of circulating mast cell progenitors is increased in patients with atopic diseases. Distinct genotypes are reported to affect mast cell/basophil activation. Objective We compared the number and function of mast cell progenitors present in the peripheral blood from donors with normal IgE (IgE < 400 U/mL) and those with atopic dermatitis accompanied by high serum IgE (IgE > 5000 U/mL). Methods Purified peripheral blood cells were cultured in serum‐free methylcellulose containing stem cell factor (SCF), IL‐6 plus IL‐3. Fresh methylcellulose containing the cytokines was layered over every 2 weeks. The cultured mast cells were retrieved from the methylcellulose and were functionally analysed. Results Mast cell colonies were distinguished at 6 weeks of culture as other colony types had been degenerated. The number of mast cell colony‐forming cells varied depending on donors and was not significantly increased in peripheral blood from the hyper‐IgE atopic patients. A significant inversed correlation was found between the number of mast cells per one colony and the ages of donors. The cultured mast cells derived from atopic patients and those from normal IgE donors equally expressed FcεRI and released histamine through FcεRI, although IL‐4 priming in vitro markedly enhanced the function of mast cells regardless of donors. Conclusions These results indicate that the number of circulating mast cell progenitors may be regulated by unknown individual factors unrelated to IgE levels. Mast cell function may be regulated largely by environmental factors, such as IL‐4, but not determined by their progenitors' genotypes.