The lymph nodes of mice actively or adoptively immunized to sheep RBC and/or chicken RBC selectively retain long-lived lymphocytes after challenge with the appropriate antigen. This retention is demonstrable within 8 hr of the time of stimulation, though it probably begins even before this, and it is essentially complete within the first 24 hr. A similar selective retention is seen in nodes regional to the injection of some nonimmunogenic substances such as turpentine, but not others such as colloidal carbon or syngeneic RBC.
In animals adoptively immunized to sheep and chicken RBC simultaneously, there is a preferential accumulation of the labeled long-lived lymphocytes of donors immunized to sheep RBC in lymph nodes challenged with sheep RBC, and a preferential accumulation of lymphocytes (labeled with a different radioisotope) from donors immunized to chicken RBC in lymph nodes challenged with this antigen. This immunologically specific component is demonstrable whether the antigen is given before or after adoptive immunization, suggesting that the only labeled cells capable of specific localization in this system are those cells that normally remain in the recirculating pool. In the present experiments, 31 out of 31 sets of antigenically stimulated lymph nodes have shown radiochemical evidence of immunological specificity in the distribution of donor lymphocytes between them, while corresponding sets of nonstimulated lymph nodes have shown only small random variations in the distribution of donor cells. Two different mechanisms are postulated whereby antigenic stimulation can alter the traffic of recirculating long-lived lymphocytes through stimulated lymph nodes. One affects recirculating cells of a particular immunological specificity, while the other affects recirculating cells without regard to their immunological specificity.