{'fraction_non_alphanumeric': 0.025943396226415096, 'fraction_numerical': 0.024764150943396228, 'mean_word_length': 5.148550724637682, '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}}
Mast cells in infection and immunity

Mast cells remain one of the most enigmatic cells in the body. These cells secrete significant amounts of numerous proinflammatory mediators which contribute to a number of chronic inflammatory conditions, including stress-induced intestinal ulceration, rheumatoid arthritis, interstitial cystitis, scleroderma, and Crohn’s disease (6, 14, 24, 76). Mast cells are also prominent in the development of anaphylaxis (14, 24, 76). Yet despite the negative effects of their secretions, mast cells or mast cell-like cells have been described even among the lowest order of animals (31). The phylogenic persistence of these cells through evolution strongly suggests that they are beneficial in some fashion to the host. Mast cells are selectively found in relatively large numbers adjacent to blood or lymphatic vessels but are most prominent immediately beneath the epithelial surfaces of the skin and the mucosae of the genitourinary, gastrointestinal, and respiratory tracts. Estimated concentrations of mast cells range from 500 to 4,000 per mm 3 in the lungs, 7,000 to 12,000 per mm 3 in skin, and 20,000 per mm 3 in the gastrointestinal tract (76). Because many of these sites also happen to be portals of infection, mast cells may represent one of the first inflammatory cells encountered by an invading pathogen. There is considerable evidence that mast cells recognize and react to a wide range of microorganisms or their products (Table 1). Such interactions lend further credence to the notion that mast cells have the potential to markedly influence the course of microbial infections. In this paper, we review data that support the possibility that the