Potentiation of lymph node antibody synthesis by normal thymus in vitro.

Antibody formation during the secondary response was enhanced when normal thymus fragments from 1- to 2-week-old rabbits were coincubated with immune popliteal lymph node fragments. Although the addition of three thymus fragments to three lymph node isolates produced a significant increase in antibody synthesis, six or nine thymus fragments stimulated the response still further; normal spleen or normal lymph node did not stimulate. Radioactive amino acid incorporation into antibody confirmed that antibody synthesis was potentiated by the thymus. In addition, increased synthesis of total globulins was quantitatively measured. The thymus seemed to enhance formation of only 7S immunoglobulin as determined by sucrose gradient centrifugation. It is not known whether thymus cells, humoral factors, or both participate in this response, or what intracellular metabolic events are being stimulated when the thymus is added to the cultures.