ADULT THYMECTOMY PREVENTION OF APPEARANCE OF SUPPRESSOR T-CELLS WHICH DEPRESS CONTACT SENSITIVITY TO PICRYL CHLORIDE AND REVERSAL OF ADULT THYMECTOMY EFFECT BY THYMUS EXTRACT

Suppressor cells, which depress the passive transfer of contact sensitivity appear in the lymph nodes and spleen of mice injected with picryl sulfonic acid (PSA). These cells produce a soluble suppressor T[thymus-derived]-cell product (s-TCP), and immune lymph node cells incubated in s-TCP fail to transfer contact sensitivity. The appearance of suppressor T cells following the injection of PSA was prevented by adult thymectomy (ATx). ATx also limited the production of s-TCP. ATx had no effect on the DNA synthesis which occurs in the lymph nodes of mice injected with PSA. The adverse effect of ATx on suppressor cells was completely reversed by a neonatal thymus graft placed under the renal capsule, the effect was partially reversed by grafts given 600 r in vitro, and to a limited extent by grafts given 1000 r. The injection of thymus extract also reversed the effect of ATx, whereas splenic extract was inactive. The suppressor T cell which depresses contact sensitivity is probably dependent on the presence of the thymus because it requires a thymus hormone, and not because it belongs to a short-lived population which is rapidly renewed by cells coming from the thymus.