{'fraction_non_alphanumeric': 0.02572347266881029, 'fraction_numerical': 0.04340836012861737, 'mean_word_length': 4.845070422535211, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Cleavage of the low‐affinity receptor for human IgE (CD23) by a mite cysteine protease: Nature of the cleaved fragment in relation to the structure and function of CD23

Der p I, a cysteine protease representing a major allergen of the house dust mite Dermatophagoides pteronyssinus, has recently been shown to cleave CD23 from the surface of cultured human B cells (RPMI 8866 B cell line). We have now undertaken a detailed investigation of CD23 cleavage by Der p I. We demonstrate that Der p I cleaves CD23 at two sites (Ser155‐Ser156 and Glu298‐Ser299) to produce a 17‐kDa fragment containing the lectin domain and only part of the C‐terminal tail. No such effect was demonstrable with mouse CD23, a finding which was anticipated based on its lack of the cleavage sites identified on human CD23. Based on the cleavage pattern and the model of CD23, we propose a sequence of events leading to the liberation of the 17‐kDa soluble CD23 fragment. The biological significance of such cleavage is underlined by the demonstration that Der p I‐treated B lymphocytes lose their ability to bind IgE, and that the 17‐kDa fragment (amino acids 156–298) contains the minimum structural requirement (amino acids 156–288) for binding to both IgE and CD21.