Sensitization to Blomia tropicalis among asthmatic patients in Taiwan

House dust mites have been reported as one of the most important allergens in Taiwan especially in asthmatic patients. This study was conducted to determine the allergenicity of Blomia tropicalis and sensitization of asthmatic patients in Taiwan. Serial dust samples were collected every month between July 1993 and June 1994 from 13 houses of mite-allergic patients. About 1 m2 surface area of a quilt was vacuumed. The floating method was used to collect mites, then identification and counting were performed. Results showed that Dermatophagoides pteronyssinus and B. tropicalis were the two most common species of mites found in allergenic patients' houses in Taipei. D. pteronyssinus accounted for 52.1% of the total number of mites and was found in every house. B. tropicalis, although not present in every sample, accounted for 44.3% of the total number of mites. The skin test positive reaction to B. tropicalis, D. pteronyssinus and Dermatophagoides farinae were 73.3, 88.3 and 85.0% as determined from 60 allergic patients who attended our allergy clinics. The extract prepared from B. tropicalis was used to determine the allergenicity and contained at least 30 protein components when silver stained. The most frequently detected allergens were proteins with molecular weights of 14.3, 106.5, 94.0, 72.0, 91.9, 63.7, 100.3, 43.6, 27.3, 62.0, 34.7, 18.3, 41.1 and 21.9 kD. The frequency of IgE binding of patient sera to those proteins were 87.0, 65.2, 56.5, 43.4, 39.1, 39.1, 34.8, 30.4, 30.4, 17.4, 17.4, 17.4, 13.0 and 8.7%. The results from immunoblot inhibition showed that there was IgE cross-reactivity among the B. tropicalis and D. pteronyssinus. However, there were two major allergenic components of B. tropicalis not inhibited by D. pteronyssinus with molecular weights of about 14.3 and 27.3 kD. The use of B. tropicalis extract for diagnostic purposes to identify patients with specific sensitivity should be considered in Taiwan.