Induction of T-lymphocyte differentiation by thymic epithelial cell monolayers

Abstract

Thymic epithelial (TE) cell monolayers were established from single cell suspensions of human thymus, and their induction of T-lymphocyte differentiation was studied. After exposure to TE cell monolayers, human bone marrow lymphoid cells showed a marked increase (97%) in the number of T lymphocytes. Supernatants from TE cell cultures were also effective, and the response was similar to but greater than that obtained by incubation with thymosin. Peripheral blood lymphocytes from normal adults did not show an increase in T lymphocytes following exposure to TE cells. However, T lymphocytes in peripheral blood from seven of eight immunodeficient patients with T-lymphocyte defects increased strikingly after contact with TE monolayers. In four of these patients, supernatants from TE cell monolayers and thymosin also induced T-lymphocyte maturation; in three, direct contact with the TE monolayer was required. The method used for establishing TE cell monolayers permits the growth of TE cell cultures devoid of thymocytes. These TE monolayers may then be used not only to study T-lymphocyte differentiation in vitro, but also to assess T-lymphocyte precursors in immunodeficient patients. Supernatants from TE cell monolayers or the cultured TE cells themselves may have value in the treatment of immunodeficiency syndromes.