Abstract
Thymectomy, splenectomy and/or lymphadenctomy affect antibody synthesis to a soluble antigen, hemocyanin, in bullfrog larvae. Tadpoles were divided into seven groups and these into three subgroups: Experimentals— A: operated and immunized by hemocyanin or allografts; Controls—B: operated but non‐immunized; Controls—C: one group unoperated and immunized. With regard to the spleen, good correlation between antibody titer and degree of splenic regeneration was observed. Structurally, the white pulp contained numerous small lymphocytes but in the red pulp, the number of blast cells and lymphocytes increased. The spleen may be the main organ involved in larval antibody synthesis. The lymph glands seem secondary; lymphadenectomized larvae showed no regeneration of lymph glands and antibody titers were lower than in sham‐operated controls. Compensatory hypertrophy of the remaining gland in unilaterally lymphadenectomized larvae was absent. With regard to cell types, lymph glands showed a picture similar to active nodules, i.e., the core of the cords consisted of blast cells and larger lymphocytes surrounded by layers of small lymphocytes. Thymic regeneration occurred in all tadpoles and, of much interest, titers were always highest in this previously thymectomized group. Observations on thymectomized tadpoles suggest a thymus stimulating effect on certain peripheral lymphoid organs, notably the spleen. The thymus in frog larvae may be important in antibody synthesis during later stages when the capacity to develop cellular immunity has already matured.