Staircase Rise in the Antibody-Forming Cell Population in Secondary Response

Abstract

Secondary anti-sheep RBC response by dispersed mouse spleen cells cultured in cell-impermeable diffusion chambers was assessed by the hemolytic plaque assay in combination with autoradiography and treatment with vinblastine. The results showed that, as in the spleen of mice undergoing a primary response, growth of the antibody-forming cell population occurred non-randomly in a staircase manner and recruitment of precursor cells into the antibody-forming cell population occurred repeatedly in a non-random manner. However, the size of the recruitment was significantly larger than that in the spleen of mice undergoing a primary response (i.e., a maximum of 40-fold vs 4-fold). Further studies on these precursor cells indicated that they transform into antibody-forming cells after a short but distinct lag following completion of mitosis. Another important observation was that the antigen-triggered proliferation of immunocompetent precursor cells could have occurred as early as 30 min after exposure of dispersed spleen cells to the test antigen, in contrast to a lag of more than 10 hr in the spleen of mice undergoing a primary response.