Thymic factors and T cell maturation in vitro : A comparison of the effects of thymic epithelial cultures with thymic extracts and thymus dependent serum factors

In the present review the results obtained so far with thymic epithelial culture supernatants (TES) or cocultivation of potential precursor T cells with TE cells will be discussed and compared with the effects reported for other thymic factors in studies on T cell differentiation in vitro. These studies can be divided into those involved with T cell markers, T cell proliferative capacity and effector T cell functions. In sections 4, 5 and 6 the effects of thymic factors, TES and TE cells with regard to their capacity to modify these three T cell parameters in vitro will be summarized. Since it has not yet been conclusively demonstrated which are the target cells for the action of thymic factors, the putative target cells will be dealt with separately in each section. Additionally, I will present some of our recent data with TES which support the suggestion that factors present in TES can induce maturation of the subpopulation of immature thymocytes, the peanut-agglutinin (PNA)-agglutinating, corticosteroid-sensitive cells with a high density of Thy 1-antigen. The TES used routinely in our studies is derived from rats TE cultures prepared as described in detail previously. Similar results have been obtained with human TES (A.M. Kruisbeek and G.C.B. Astaldi, unpubl. obs.) and with TES from mouse TE cultures derived from mice syngeneic to the mice used as target cell donors for the experiments shown here (A.M. Kruisbeek, unpubl. obs.). However, mouse TES is more difficult to obtain because cultures tend to be rapidly overgrown by fibroblasts, reason why for routine studies (once it was established that no differences between xeno- and syngeneic TES were observed) the rat TES is preferred. Chemicals/CAS: Antigens; Concanavalin A, 11028-71-0; Cortisone, 53-06-5; Phytohemagglutinins; Thymic Factor, Circulating, 78922-62-0; Thymus Extracts; Thymus Hormone