beta-D-glucans from basidiomycete strains are powerful immunomodulatory agents in several clinical conditions. Therefore, their assay, purification and characterization are of great interest to understand their structure-function relationship. Hybridoma cell fusion was used to raise monoclonal antibodies (Mabs) against extracellular beta-D-glucans (EBGs) from Pleurotus ostreatus. Two of the hybridoma clones (1E6_1E8_B5 and 3E8_3B4) secreting Mabs against EBGs were selected. This hybridoma cell line secreted Mabs of the IgG class which were then purified by hydroxyapatite chromatography to apparent homogeneity on native and SDS-PAGE. Mabs secreted by 1E6_1E8_B5 clone were found to recognize a common epitope on several beta-D-glucans from different basidiomycete strains. This Mab exhibited high affinity constant (K-A) for beta-D-glucans from several mushroom strains in the range of 3.20 x 10(9) +/- 3.32 x 10(3)-1.51 x 10(13) +/- 3.58 x 10(7) L/mol. Moreover, they reacted to some heat-treated beta-D-glucans in a different mode when compared with the native forms; these data suggest that this Mab binds to a conformational epitope on the beta-D-glucan molecule. The epitope-binding studies of Mabs obtained from 1E6_1E8_B5 and 3E8_3B4 revealed that the Mabs bind to the same epitope on some beta-D-glucans and to different epitopes in other antigen molecules. Therefore, these Mabs can be used to assay for beta-D-glucan from basidiomycete mushrooms. (C) 2015 Elsevier Ltd. All rights reserved.