The effects of BCG on both cellular and humoral immunity during the early response to a hapten carrier complex.

Cell-mediated reactions to the carrier and antibody-mediated reactions to hapten and carrier were studied in guinea-pigs treated with a single i.v. injection of BCG at different intervals of time before immunization with two different doses of a hapten-carrier complex. The results clearly show that BCG-induced delayed hypersensitivity reactions to the carrier and decreased antibody synthesis to the hapten. It is proposed that BCG acts on a dispatcher cell which controls both cellular and humoral immunity.