ABSTRACT
The mechanisms by which antigen stimulates and directs the highly complex series of cellular and molecular events involved in an immune response still remains largely unknown. After presentation of antigen to the lymphoid tissue, an individual may respond in a number of different and distinct ways including the production by lymphoid cells of humoral antibody of one or more immunoglobulin classes; sensitization of cells to mediate delayed hypersensitivity reactions without detectable humoral immunoglobulin synthesis; or specific tolerance may ensue so that subsequent immunologic challenge with the same antigen does not stimulate either antibody formation or cellular immunity. The chapter deals with some of the cellular and molecular events occurring during the induction and maintenance of immunologic tolerance to Shigella paradysenteriae as studied in this laboratory. It discusses the role of various cell classes in both immunity and tolerance to this microorganism and the involvement of immunogenic RNA in antibody formation.
