SUMMARYNeonatal spleen populations have been studied for antigen‐binding capacity in an attempt to determine if the frequency of double antigen‐binding cells changes as the population matures. Just after birth, the frequencies of total ABC, double ABC and Ig‐bearing cells were similar to the frequencies seen in the adult bone marrow. During the first week after birth, the proportion of total ABC and Ig‐bearing cells rose sharply so that by 8 days after birth, these cells were about half of adult levels. The proportion of total double ABC, after a brief rise at day 1, remained constant throughout the test period. Thus, the proportion of total ABC which are doubles gradually decreases with age. Sedimentation velocity studies indicate that double ABC's tend to co‐sediment with cells which require a period of maturation before they can respond to a thymus‐independent antigen in irradiated hosts. Single ABC, on the other hand, tend to co‐sediment with cells which are immediately responsive to antigen, or require a shorter maturational period before they become responsive to antigen. All of these data, taken together with our other work, suggest the possibility that multiple ABC are clonally‐derived lymphocyte populations which become more restricted in their antigen‐binding capaci
展开▼
