Surface immunoglobulin phenotype of murine spleen cells which form B cell colonies in agar

Separation of IgD‐bearing B lymphocytes from the spleens of 3‐week‐old or adult mice has been achieved using cellular affinity columns and an anti‐δ allotype serum. The results demonstrate that the majority of cells capable of forming B lymphocyte colonies in agar are δ‐positive although they lose detectable IgD upon stimulation. It is proposed that these cells are the descendants of IgD‐negative cells found in the fetal liver and neonatal spleen.