Determinations of the rates of antibody synthesis during first, second, and hyperimmune responses to bovine gamma globulin using S35-labelle aminod acids indicate the following:
1. In all three responses the rate of antibody synthesis increases while antigen is circulating and then begins to decline rapidly after elimination of detectable circulating antigen.
2. The initial rates of decline of antibody synthesis are approximately the same for all three responses.
3. There is a relatively persistent source of antibody production which appears after repeated stimulation and increases in proportion to the number of repeated stimuli.