Antigens and allergens in Dermatophagoïdes farinae mite. II. Purification of AG f1, a major allergen in Dermatophagoïdes farinae.

Ammonium sulphate precipitation and DEAE chromatography is an efficient way of purifying Ag 11, the main allergen in mites, which has already been characterized by crossed radioimmunoelectrophoresis. At 60% of saturation in ammonium sulphate, a precipitate is formed which, dissolved and dialysed has been named fraction A 60. It is mainly composed of Ag 11. In the fraction DE obtained by DEAE chromatography of the ammonium sulphate fraction A 60, Ag 11 appears homogeneous on crossed-immunoelectrophoresis. Isoelectrofocusing results indicate an average isoelectric point near neutrality in agreement with the non-absorbtion of Ag 11 on the DEAE cellulose at a weak ionic strength (0.01, at pH 7.2). By sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration Ag 11 has a molecular weight of 28,000. Ag 11 appears as a single polypeptidic chain with numerous dithio-bonds implying a highly folded and resistant structure. Oligosaccharides could be present as constituting molecules as well as contaminating ones as was assumed for hexosamines. These results are discussed with reference to a similar study performed on the major allergen of . The allergenic properties of Ag 11 as present in fraction DE were tested by RAST-based methods. Fraction DE is an inhibitor as good as Df 80d and when it is coated on paper discs it can bind specific IgE in sera from the majority of mite sensitive patients. The results suggest that Ag 11 is a major allergen from .