ELECTROPHORETIC CHARACTERIZATION OF WHEAT-GRAIN ALLERGENS FROM DIFFERENT CULTIVARS INVOLVED IN BAKERS ASTHMA

In order to identify and characterize the wheat grain allergens involv ed in bakers' asthma, proteins were sequentially extracted from whole- meal flour. The polypeptide composition of the individual solubility f ractions (albumin/globulin, gliadin and glutenin) was analyzed by sodi um dodecyl sulfate-gel electrophoresis (SDS-PAGE), and high-resolution two-dimensional gel electrophoresis with immobilized pH gradient 4-9 in the first dimension (IPG-Dalt). The resolved polypeptides were tran sferred onto an immobilizing polyvinylidene difluoride membrane and in cubated with a pooled serum from four asthmatic bakers. Bound IgE was demonstrated by autoradiography using I-125-labeled anti-human IgE. Ou r study demonstrated that the serum of the bakers allergic to flour co ntained IgE antibodies which bound to numerous polypeptides of all thr ee solubility fractions. The highest percentage of IgE binding was obs erved with certain albumin and/or globulin polypeptides, whereas the g liadins and glutenins exhibited considerably less allergenicity. SDS-P AGE revealed that the protein which bound the highest percentage of Ig E from the sera of the allergic bakers is a 27 kDa albumin. More detai led investigations using IPG-Dalt demonstrated that this allergen is n ot a single polypeptide but consists of several polypeptide spots that differ in their isoelectric points. Quantitative studies using comput er-assisted laser densitometry revealed that the amount of patients' I gE bound by these particular polypeptides differed considerably betwee n the seven wheat cultivars examined, ranging from 13% to 53% of the t otal radioactive uptake.