CHAPTER II - IMMUNITY AND TOLERANCE: THE CURRENT CONCEPTS

Abstract

This chapter discusses immunity and tolerance. Immunity in the medico-biological sense has come to be concerned primarily with the acquired and specific resistance to infection that follows experience of the microorganism responsible, whether as overt disease, subclinical infection or immunization with nonliving antigens. For historical and methodological reasons, intellectual interest in immunity has been centered around the nature and mode of synthesis of antibody. Insofar as cell-based immune reactions have a specificity of the same quality as antibody, this approach is justifiable and must be used as the basis for any general consideration of immune mechanisms. Natural tolerance is essentially limited to all the potential antigenic determinants present in the environments in which primary differentiation of stem cells to immunocytes takes place. These certainly include the thymus. It is not wholly excluded that all tolerance may be based on the thymus, but it is more likely that both the GAL tissues and the equally undefined regions other than the anatomical thymus, where T-D immunocytes may arise from stem cells in later life, also play their part. As they have not yet become available to experimental study, it is legitimate to assume that the processes are basically similar to those in the thymus.