Effect of Thymus-Derived Lymphocytes on Amount and Affinity of Anti-Hapten Antibody

In recent years two classes of lymphocytes have been shown to participate in specific antibody responses in mice. One class of these cells, which has migrated through the thymus and is consequently referred to as “thymus-derived,” does not secrete detectable quantities of antibody but nevertheless interacts with antigen in a specific way. As a consequence of this interaction, the second class of specific cells, the bone marrow-derived lymphocytes, are more easily stimulated. The latter cells are the direct precursors of antibody-secreting cells (1–3). Antibody affinity is a term used to describe the energy of interaction of antigen, usually hapten, and antibody. It is, of course, a character determined by the structure of the antibody (and that of the ligand); affinity should therefore be a marker of the bone marrow-derived cell population, which is directly responsible for the production of the antibody. In the current paper we show that thymus-derived cells play a major role in controlling the production of high affinity anti-hapten antibodies in response to immunization with hapten-protein conjugates. This suggests that the action of thymua-derived cells is important in increasing the rate of change of the population of precursors of antibody-forming cells upon which antigen-driven selection is operating.