Relative Pool Size of Potentially Competent Antibody-Forming Cells of Primed and Nonprimed Spleen Cells Grown in in Vivo Culture

Abstract

Summary Spleen cells from primed and nonprimed donors were cultured in lethally irradiated, isologous recipients and the relative pool size of PC cells was determined at varying intervals for 13 days under various experimental conditions. The results showed that the pool size of PC cells decreased to a minimum during the first 5 days after culture of nonprimed spleen cells. This decrease in pool size can be circumvented almost completely by the combined treatment of reduced radiation exposure to recipients and bone marrow therapy. It can be accentuated by exposing these cells to a noncross-reacting antigen when spleen cells are known to be proliferating and differentiating into terminal blood cells maximally. In contrast, the pool size of PC cells from primed donors neither increased nor decreased significantly during this period of observation and, furthermore, was not affected by these treatments. These results indicate that there exist, in accordance with the unidirectional flow model, at least two sequential compartments of PC cells, PC1 and PC2. Cells in the former compartment can be considered to be multipotent—capable of differentiating along several paths depending upon the stimuli—and those in the latter unipotent and therefore insensitive to hematopoietins and unrelated antigenic stimuli.