Requirements for growth of immature thymocytes from fetal and adult XXXX in vitro.

@entity2047 @entity19 @entity3019 @entity4515 @entity5003 @entity1360 @entity1961 @entity3414 @entity4514
We report here defined culture conditions that allow reproducibly the growth of the majority of immature thymocytes from both fetal (14-15 days of gestation) and adult @entity19 . The combination of @entity4514 ( @entity4515 ), @entity1360 and recombinant @entity2047 ( @entity2047 ) is both sufficient and necessary to induce growth of about 1/6.2 (range 1/3-1/9) and 1/4.3 (range 1/2-1/7) immature thymocytes from adult and fetal @entity19 , respectively, in serum-free cultures. Several other combinations tested (e.g. @entity4515 + @entity2047 , concanavalin A + @entity2047 ) were poorly or not active. None of the agents tested alone ( @entity4515 , @entity1360 , concanavalin A, pokeweed mitogen, @entity2047 ) had any effect. We found no evidence for a role of @entity5003 and @entity3019 on growth of these cells. The growth of activated immature thymocytes from either fetal or adult @entity19 was inhibited by a monoclonal antibody against @entity19 @entity2047 receptors. Under the same conditions that stimulated growth of most immature thymocytes, they did not mature into cells expressing @entity3414 , @entity1961 or T cell antigen receptor (KJ16) after 7 to 15 days of continuous proliferation in culture. Nor did they give rise to cells with cytolytic activity after 7-9 days of culture. In some but not all experiments cultures of immature thymocytes from adult @entity19 but not from fetal @entity19 generated cells (1 out of 120-310) with helper function for B lymphocytes. While we confirmed here that approximately 50-70% freshly isolated immature thymocytes express receptors for @entity2047 , our results indicate that these cells need to be activated (by e.g. @entity4515 + @entity1360 ) to respond to @entity2047 . A possible mechanism to account for the expression of nonfunctionally competent @entity2047 receptors is proposed and our results concerning the maturation of immature thymocytes in vitro are discussed.
