Abstract
Exposure of antibody to relatively high concentrations of uranium yielded an electron-dense specific localizing reagent. Destruction of antibody activity during labelling was prevented by protection of the antibody-antigen combining sites: Anti-Bordetella bronchiseptica antibody was removed from serum by absorption with B. bronchiseptica. The washed agglutinate was exposed to uranium. The antibody recovered from this agglutinate by brief alkali treatment in the cold was 80 to 100% pure and contained 28 to 312 atoms of uranium per unit of 156,000 molecular weight. The material stained the walls of living or formalin killed, and the cytoplasm of living B. bronchiseptica. E. coli and mouse spleen cells were not stained. Contrast was diminished when B. bronchiseptica was exposed to unlabelled anti-B. bronchiseptica antiserum prior to uranium-antibody conjugate. Absorption with B. bronchiseptica, but not with E. coli, abolished the staining capacity of purified uraniumn-antibody conjugate. Whole antiserum labelled with uranium without specific protection, even though retaining some antibody activity, was not suitable as a stain since it deposited a large amount of debris and apparently stained both E. coli and B. bronchiseptica.