• T cell subsets;
  • T cell ontogeny;
  • thymic hormone;
  • T suppressor;
  • T helper

ABSTRACT: The influence of thymic preparations on the kinetics of the development of PFC response to sheep erythrocytes was tested in mice 0 to 4 weeks old. Soluble thymic factor (STF) or thymic epithelial culture supernatant (TES) was prepared from the thymuses of C57B1/6 mice. STF was injected to gravid mice on day 13 or on day 18 of gestation. A marked acceleration in the appearance of PFC to SRBC was noted only in the offspring from those mothers having received STF on day 18. The ability to generate anti-SRBC response in vitro by splenocytes from 1-to 4-week-old mice was significantly improved in the presence of TES. The accelerated appearance of the response to a T-dependent antigen is attributed to increase in the ratio of T helper/T suppressor cells resulting from differentiation and/or clonal expansion under the influence of STF crossing of the placental barrier in the materno-fetal direction.