ABSTRACT
Peripheral blood lymphocytes can be stimulated to undergo a series of changes in culture by a variety of substances including increased phospholipid uptake, increase in RNA synthesis, protein synthesis, blast transformation, deoxyribonucleic acid synthesis and mitosis. Presence of circulating lymphocyte inhibitor in the serum supported a growing concept that there were naturally occurring immunosuppressive substances regulating the immune response. This chapter reviews the concept of humoral immunoregulation, examines technical factors possibly affecting results of these studies. It analyzes reports of circulating lymphocyte inhibitors in liver disease and uremia. Inhibitors of other lymphocyte activities in vitro, such as lymphocyte-mediated cytotoxicity and E-rosetting assay, will also be reviewed. Humoral immunoregulation could be mediated by naturally occurring serum factors that have been shown as mitogenic and able to enhance lymphocyte functions in vitro. Different methods of separating lymphocytes for culture influence the amount of formed cellular elements contaminating lymphocyte suspensions and the relative proportions of lymphocyte subpopulations isolated.
