Regulation of Antibody Formation by Serum Antibody

Rabbits were immunized to two antigens and 18-55 days later exchange transfusion was performed using blood of rabbits immunized to one antigen only. By this means, serum antibody levels to one antigen were reduced 50-84% while maintaining serum antibody levels to the second antigen. After exchange, serum antibody levels of the removed antibody rose rapidly for 24-48 hr and then more slowly, reaching peak titers an average of 8 days later. The peak titer was 48-222% higher than the preexchange titer. The specificity of this rebound excluded as a cause nonspecific changes in Ig levels. Passive administration of antibody to a third antigen 4-7 days before the exchange indicated that re-equilibration of preformed antibody was not a major factor in the rebound. A change in the ratio of IgM to IgG antibodies as a cause of an increased neutralization titer in the postexchange sera was also excluded. It was therefore suggested that a change in the rate of antibody formation had occurred, although other changes in the quality of serum antibody were not excluded.