Immunological Properties of a from of Non-Precipitating Diphtheria Antitoxin Which Does Not Sensitize Human Skin

Abstract

A type of human non-precipitating diphtheria antitoxin is described which is not able to cause immediate wheal reactions in appropriate recipients. Individuals who form this antitoxin following a booster dose of toxoid develop no immediate reactivity upon subsequent testing with intradermal toxoid. The sera of ten persons who formed only non-precipitating non-skin-sensitizing antitoxin were studied in detail and the following characteristics were observed. No fixation of complement occurred unless large amounts of antitoxin were used, and specific coprecipitation of antitoxin in two high titered sera resulted upon the addition of precipitating antitoxin and toxin. None of the sera tested were able to sensitize human skin, nor was there any evidence that this antitoxin remained at intradermal sites. When three sera containing the highest titers were separated electrophoretically, the antitoxin was found to migrate as a slow-moving gamma globulin (γ₂). Three of seven sera were able to inhibit immediate reactions at sensitized sites when combined with equivalent amounts of toxoid. Four sera could not be evaluated for this property because they had an irritative effect when injected alone in the skin.