Study of the effect of single or multiple doses of BCG on antibody-dependent cellular cytotoxicity

The in vivo effects of BCG were studied on antibody-dependent cellular cytotoxicity (ADCC) using an assay in which the effectors were spleen cells of BCG-treated mice, and the targets antibody-coated chicken red blood cells (CRBC). In the study of the time course of action, an increased ADCC-activity was observed starting at day 10 with a maximum (four-fold augmentation) at day 14 after BCG treatment. The nature of the effector cell was investigated: in normal mice the activity was found in two cell populations, i.e. macrophages and theta-negative (theta-) nylon-adherent spleen cells. A BCG treatment increased the ADCC activity of macrophages of theta- nylon-adherent spleen cells and induced a population of theta- nylon-non-adherent spleen cells. In old mice, the effects of BCG were compared after a weekly long-term (6 months) treatment and after administration of a single dose. It was concluded that ADCC is higher in old mice than in young mice and can be further increased by treatment with a single dose of BCG in contrast with the long-term treatment which impaired this immune reaction.