| Abstract: | The cellular production of two rabbit γ-globulin allotypic specificities, A4 and A5, determined by allelic genes was investigated by the fluorescent antibody method. The 7S γ-globulin fractions of precipitating antisera were conjugated to fluorescein isothiocyanate and to lissamine rhodamine B sulphonyl chloride. Frozen sections of lymph nodes from eighteen rabbits, A4—A4 and A5—A5 homozygotes and A4—A5 heterozygotes, were studied after exposure to the fluorescent antibody conjugates. The conjugates, each specific for antigenic determinants of 7S γ-globulin, reacted specifically with the cytoplasm of plasma cells and intrinsic cells of the germinal centres. The rabbit anti-A4 conjugate reacted only with lymph node cells of A4—A4 and A4—A5 rabbits; the rabbit anti-A5 conjugates reacted only with cells of A5—A5 and A4—A5 rabbits; the horse anti-rabbit γ-globulin conjugates reacted with cells of all three genotypes. By a variety of techniques, identical cellular localization of the two allotypes, A4 and A5, was found in the A4—A5 heterozygotes. Less than 1 per cent of the cells in any heterozygous lymph node section contained one allotype without the other. |
