Recombinant interleukin 4/BSF-1 promotes growth and differentiation of intrathymic T cell precursors from fetal mice in vitro.

Abstract

Recombinant mouse interleukin 4/BSF‐1 (rIL4/BSF‐1) together with phorbol myristate acetate (PMA) promotes growth of one out of approximately four intrathymic T cell precursors from fetal mice (14‐15 days gestation). This response is not inhibited by even high concentrations of monoclonal antibody against the receptor for interleukin 2. Fetal thymocytes activated by rIL4/BSF‐1 plus PMA give rise to cytolytic T cells after 7‐21 days of culture. All the proliferating cells are Thy1+, some of them express Lyt2 but none has detectable L3T4 T cell differentiation antigens nor T cell antigen receptor (F23.1) on the cell membrane as assessed by immunofluorescence staining and flow fluorocytometry analysis. It is concluded that rIL4/BSF‐1 exerts both growth and differentiation activities on normal intrathymic T cell precursors. The results provide evidence for an alternative growth factor to interleukin 2 involved in proliferation of T cell precursors. These findings open new and direct ways of studying cellular and molecular events during the differentiation of normal intrathymic T cell precursors in vitro and extend the spectrum of target cells for IL4/BSF‐1.