Guinea pigs sensitized with tubercle bacilli demonstrate a dual allergic response mediated by two chemically distinct plasma fractions:
1. Antibody to tuberculopolysaccharide is located exclusively in fraction II (gamma globulin). This fraction will passively transfer systemic anaphylaxis and urticarial type skin reactivity to tuberculopolysaccharide, and contains the Middlebrook-Dubos antibody.
2. Antibody to tuberculoprotein is contained exclusively in a new plasma fraction called fraction IV-10. By Cohn's Method X, fraction IV-10 is a part of fraction IV (alpha globulin) and to a lesser extent V (albumin). This fraction will passively transfer to normal guinea pigs a delayed type skin sensitivity to tuberculin PPD which is maximal between 18 and 30 hours, and it contains the Boyden antibody.
When fractions II and IV-10 are combined, the antibody to tuberculopolysaccharide inhibits the passive transfer of delayed type reactivity. Combination of these two fractions does not alter their separate in vitro hemagglutinating properties. Adsorption of IV-10 with Boyden sensitized cells removes its ability to transfer delayed type tuberculin sensitivity. Adsorption of II with Middlebrook-Dubos-sensitized cells removes its capacity to effect passive transfer of immediate type reactivity to tuberculopolysaccharides.