Allergen discs prepared from nitrocellulose: detection of IgE binding to soluble and insoluble allergens

Nitrocellulose discs, 6 mm in diameter, are suggested as an alternative to cyanogen bromide-activated paper for the coupling of allergens in radio- or enzyme-linked assays to estimate allergen-specific IgE in serum. The preparation of allergen discs with nitrocellulose is simple, involving 3 steps: (a) drying allergen extract onto disc, (b) soaking discs in a 3% solution of bovine serum albumin, and (c) washing out the buffer. Very similar results (r = 0.94) were obtained using either paper or nitrocellulose discs for radioallergosorbent testing of sera from 15 bakers using allergens from mites, ryegrass pollen or wheat grain. The amount of protein (as radiolabelled albumin) actually bound to either type of disc or microtitre trays was similar, and low (5% of the protein applied for each media). However, when the protein was applied to nitrocellulose in 1% KOH up to 70% of it was bound. This solvent permitted better evaluation of IgE binding to insoluble allergens such as glutenin, which proved to be the most allergenic wheat-grain fraction tested by this method for a group of 9 bakers.