Urea as a Solvent in Preparation of Antigen Extracts

Abstract

The development of the study of allergy in recent years, and particularly the search for the etiologic factors, has focused attention upon numerous protein containing substances. These include foods, pollens, molds, epidermal structures, orris root, house dust and such less common factors as the scales on sand flies or the stinging organ of bees, wasps, etc. The substance suspected may be tested on the patient in various ways: (a) by direct application of it to the skin, to the conjunctivae, or if a food, it may be ingested; (b) the juice may be expressed from certain of the substances and used by application to a scratch on the skin, or by intracutaneous injection. This method is naturally limited in its application. The ideal method is one which would concentrate the active substance, change its physical or chemical composition little or none, and one which could be used on all types of substances. By analogy with immunologic phenomena, and in view of the evidence which has accumulated in the field of allergy, one is led to believe that the active allergic agent is protein or closely attached thereto.

Proteins in general are rarely water soluble to any extent; this is especially true after they have undergone the procedures necessary to separate them from the various substances mentioned above. The simplest extraction methods employ a solution of NaCl in various concentrations. Alkalies, notably a bicarbonate or hydroxide, or a neutral phosphate buffer solution, find most general use. Recently a glucose extract has been advocated. The multiplicity of methods indicates that none is entirely satisfactory. This fact led to the present attempt to utilize the peculiar solvent action of strong urea solution in the preparation of these and other active extracts.