Frequency and avidity of specific antigen-binding cells in developing mice.

In order to analyze the development of antibody diversity in which the genes coding for the antigen-specific cells we have compared the binding of diverse antigens by cells in the fetal, neonatal, and adult mouse. Although the numbers of antigen-binding cells present in fetuses and young animals were smaller than in adults, no restriction could be detected in the varity of specificities expressed in the fetuses, either with respect to the kinds of antigens bound, or to the range of avidities of binding. Cells specific for each of the 11 antigens tested could be detected in the fetus only in the last 4 days before birth, at which time they appeared both in the liver and in the spleen. In all cases, these cells disappeared both in the liver and in the spleen. In all cases, these cells disappeared from the liver within a day of birth, but continued to increase in number in the spleen until adulthood...