Functional maturation of neonatal spleen cells.

Maturation of neonatal spleen cells was studied in vitro with a cell population restricted with respect to functional properties. It is shown that the onset of the immune response to SRBc in post-natal mice was delayed because B and T cells were incompetent. It appears, however, that the development of these two cell populations does not occur in parallel. Since the addition of adult macrophages failed to overcome the incompetence of neonatal B cells in the presence of a T cell replacing factor, it is suggested that the late appearance of immune competence is due to the inability of B cells to process a T-cell signal.