Nuclear localization of bovine immunoglobulin G (bIgG) in the liver of rats injected with hydrocortisone-bIgG conjugate intravenously.

Abstract:  Bovine serum albumin conjugated with steroid hormone injected intravenously into rats can enter the hormone-target cell nuclei with its antigenicity kept intact (Nishimura and Nakano, 2000). Antinuclear antibodies (ANA) such as immunoglobulin G (IgG) are found in some autoimmune diseases. To confirm immunocytochemically whether immunoglobulin G (IgG) conjugated with steroid hormone enters in the hormone-target cell nuclei, bovine IgG (bIgG) was conjugated with hydrocortisone 21-hemisuccinate. The hydrocortisone-bIgG conjugate was injected into the vascular system of adrenalectomized rats. Then the rats were killed 2 or 3 h after injection to detect bovine IgG in the hormone-target cell nuclei of the liver by fluorescein-isothioc yanate labeled-anti bovine IgG antibody under confocal laser scanning microscopy. In the liver of both rats injected with hydrocortisone-bIgG, the fluorescence was observed in not only the cytoplasm but also the nuclei of liver cells. In control rat injected with bIgG, few nuclei showed fluorescence. These results demonstrate that bovine IgG conjugated with steroid hormone can enter the hormone-target cell nuclei of rat with its antigenicity kept intact, and suggest that antinuclear antibody in some autoimmune diseases may be transported from blood plasma into the nucleus.