Antigenic changes in lymph-node cells after administration of antiserum to thymus cells.

Mice of the RIII and C57BL strains were treated with rabbit antiserum to thymus (ATS), and cells of their lymph nodes were analyzed serologi-cally at intervals after treatment. While lymph-node cells of untreated mice were sensitive to the cytotoxic effect of isoantibodies against the theta antigen, lymph-node cells of ATS-treated mice showed a significantly reduced sensitivity. Three days after ATS treatment lymph-node cells of most mice were completely refractory to the cytotoxic effect of theta antibodies. Administration of normal rabbit serum elicited only a slight reduction of the sensitivity of lymph-node cells to the cytotoxic effect of theta antibodies. The results support the hypothesis that ATS treatment selectively affects a population of thymus-dependent circulating lymphocytes.