Lack of Recruitment of Antibody Forming Cells during the Late Haemagglutinin Response

IMMUNOLOGICAL memory and high concentrations of serum antibody are maintained for many months in animals immunized with various types of antigen1–2. One proposed mechanism for this lengthy immunity is that persisting antigen3 continuously triggers immune progenitor cells to form new antibody producing cells and memory cells to replace dying ones. Recent evidence, however, suggests that immunological memory may not require persistence of antigen4–5. Similarly, our results show that continued antigenic stimulation is not necessary for sustained haemagglutinin production late in the immune response.