An IgE-Mediated Allergic Reaction Caused by Mulberry Fruit

Abstract

Mulberry (Morus spp.) is a widespread deciduous tree and its fruit is commonly eaten in Korea and eastern Asia. Some reports demonstrate that mulberry fruit is a food allergen in the Mediterranean area. However, there has been no report of systemic allergic reactions after ingesting mulberry fruit in Korea. An 18-year-old boy with a mulberry fruit allergy visited our allergy clinic. He had experienced generalized urticaria, chest tightness, breathing difficulty, and abdominal cramping after ingesting mulberry fruit. The patient had a positive skin reaction to mulberry fruit extract (mean wheal size, 5 mm). We performed an ELISA to detect specific IgE antibody (Ab) to mulberry fruit extract in the patient's serum compared to those of non-atopic healthy controls and birch-sensitized individuals. Specific IgE Ab to mulberry fruit extract was detected in the patient's serum, as compared to non-atopic healthy controls. Another subject, who was strongly sensitized to birch pollen, also had a positive serum-specific IgE Ab to mulberry fruit. We performed IgE immunoblot analysis using the patient's and the other subject's sera, who had serum-specific IgE to mulberry fruit, to identify the IgE-binding component. An identical IgE-binding component to mulberry extract was detected in the two subjects at around 17 kDa, and which might be PR 10 of Bet v 1. In conclusion, mulberry fruit could induce a systemic allergic reaction through an IgE-mediated mechanism, and cross-reactivity might occur between mulberry fruit and birch pollen.

Keywords: IgE; Mulberry; allergen; food allergy.

Fig. 1. The level of specific IgE to mulberry fruit extract in the sera of our patient, birch sensitized individuals (n=31), and non-atopic controls (n=20). The positive cut-off value (1.621) was derived from the mean plus three standard deviations of readings from the non-atopic control sera. A, index patient; B, subject with positive serum specific IgE to mulberry fruit in birch sensitized individuals.

Fig. 2. Results of IgE immunoblot analysis to mulberry fruit extract. Blank, buffer control; A, patient's serum; B, serum from a subject who was strongly sensitized to birch pollen and had serum specific IgE antibody to mulberry fruit; NC, non-atopic controls.