IMMUNE-RESPONSES IN MICE AFTER GASTRIC AND SUBCUTANEOUS IMMUNIZATION WITH BCG

Mucosal immunization can induce immune responses different from those induced by systemic immunization. In this study, murine immune respons es were analysed after immunization through gastric and subcutaneous r outes with Mycobacterium bovis BCG. The number of circulating cells se creting antigen-specific immunoglobulins (Ig), and the number of gamma interferon (IFN-gamma) secreting cells in spleen-cell cultures after in vitro stimulation with mycobacterial antigens were analysed at the single cell level by the ELISPOT method. Levels of antigen-specific an tibodies in sera were determined by ELISA. In the subcutaneously immun ized mice the authors found approximately 100 times mole splenic cells secreting antigen-specific IgG than in gastrically immunized mice or control mice. Their levels of antigen-specific IgG in sera were 66-670 0 times higher than in sera from gastrically immunized mice or control mice, In contrast, the numbers of IFN-gamma producing cells in spleen -cell cultures after in vitro activation with BCG were equally high in the immunized groups of mice, and for both groups higher than in non- immunized controls, Furthermore, IFN-gamma producing cells could be de monstrated in gastrically immunized animals even without in vitro acti vation, The results demonstrate that gastric immunization with the BCG vaccine can induce a systemic T cell-mediated immune response against mycobacterial antigens.