Pollen from the Acacia has been reported as an important source of pollinosis in tropical and subtropical regions of the world. The aim of this study was to characterize the IgE binding protein of Acacia farnesiana pollen extract and evaluate cross-reactivity with the most allergenic pollens. In this study, pollen extract was fractionated by SDS-PAGE and the allergenic profile was determined by IgE-immunoblotting and specific ELISA using forty-two Acacia allergic patients. Potential cross-reactivity among Acacia and selected allergenic plants was evaluated with ELISA and immunoblotting inhibition experiments. There were several resolved protein fractions on SDS-PAGE which ranged from 12 to 85？kDa. Several allergenic protein bands with molecular weights approximately between 12 and 85？kDa were recognized by IgE-specific antibodies from Acacia allergic patients in the immunoblot assay. The inhibition by the Prosopis juliflora pollen extract was more than those by other pollen extracts. Moreover, the wheal diameters generated by the Acacia pollen extract were highly correlated with those of P. juliflora pollen extracts. The findings suggest that several proteins such as 15, 23, 45, and 50？kDa proteins could be used as diagnostic and therapeutic reagents for patients allergic to A. farnesiana and P. juliflora. 1. Introduction Acacia farnesiana (Vachellia farnesiana), a member of the Fabaceae family, is common throughout tropical and subtropical regions of Asia, Africa, Australia, and America with hot and humid climates, where it is planted as a shade and/or ornamental tree or for binding sand [1, 2]. Pollens from the Fabaceae family have been reported as an important source of pollinosis in the United States, European countries, and Asia [1–3]. Moreover, the inhalation of A. farnesiana pollen is one of the main causes of respiratory allergic diseases in semiarid countries such as Iran, Saudi Arabia, and the United Arab Emirates, where the frequency of sensitization ranges from 25% to 48% [2, 4–7]. Howlett et al. reported a high level of cross-reactivity between Acacia (wattle) and Lolium perenne (rye grass) pollen using the radioallergosorbent test (RAST) [8]. The results showed that IgE molecules which bound to Acacia pollen proteins also bound to L. perenne pollen extracts. In spite of a high rate of sensitization to Acacia pollen in Iran and neighboring countries, to our knowledge, there are few studies about the characterization of A. farnesiana pollen extract, and cross-reactivity of this plant with the five most allergenic pollens in arid and semiarid
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