Relative expression of light-chain allotypic specificities on the surface of rabbit lymphocytes as a function of age.

Lymphoid cells of heterozygous Ab4/Ab9 rabbits of various ages were stained with fluorescent anti-allotype antibodies. In foetal and newborn rabbits, the percentage of Ab-positive cells in low; it increases with age, reaching the adult value when the animals are 100 days old. The rate of increase in the percentage of Ab4-positive cells is higher than in that of Ab9-positive cells. Thus, the Ab4/Ab9 ratio, which is initially 1, increases with age and reaches 2.2. in spleen and 4 in appendix of young adult animals. We conclude that the change in Ab4/Ab9 ratio is due to differential clonal expansion which we attribute to charge-related differences in the ability of Ab4 and Ab9 receptor-bearing cells to capture antigen when environmental antigens are encountered in postnatal life.