The behavior of the immunoglobulin antigen receptor on lymphocytes was studied using both fluorescent antiimmunoglobulin antibody to detect B cells and autoradiography with radiolabeled antigens to detect antigen-binding cells. It was shown that after binding of antiimmunoglobulin antibody to the lymphocyte there was a rapid loss of surface immunoglobulin and then a progressive reappearance over 18 h. This could be quantitated using an inhibition assay for surface immunoglobulin. Similarly, after binding various dinitrophenyl-conjugated proteins or keyhole limpet hemocyanin to their specific antigen-binding cells, there was a loss of the antigen receptor from the surface and then a progressive reappearance of the receptor. The reappearance of surface immunoglobulin and of the antigen receptor proceeded at about the same rate. Repeated exposure to antibody or prolonged exposure to antigen did not diminish the capacity of the lymphocyte to re-express its receptor. These events, which follow the interaction of antigen and its receptor, are of possible importance in understanding the mechanism of triggering of the immune response and of tolerance
