Anti-immunoglobulin stimulation of murine lymphocytes: III. Enhancement of the development of responsive B cells by thymic deprivation

The development of splenic B cells that can be induced to proliferate by soluble anti-immunoglobulin (anti-Ig) reagents requires 7 to 9 months in normal mice. We have found that this age-associated response is enhanced by thymic deprivation. Both neonatally thymectomized LAF 1 mice and thymectomized, lethally irradiated, and bone marrow-restored Balb/c mice respond earlier and more strongly to anti-Ig than their sham controls. Nevertheless, at least 3–4 months are still required after thymectomy before a response can be measured. The earlier and enhanced response to anti-Ig seen in thymectomized animals is not due simply to an increase in the total number of Ig-positive spleen cells. The age-associated response of splenic B cells to anti-Ig we have observed in normal mice may be explained by the “natural” loss of thymic influence that occurs with age.