Interleukin 3 Stimulation Enhances Tyrosine Phosphorylation and Proliferative Activity of Human Fetal Thymocytes and Leukemic T-cell Precursors at Multiple Developmental Stages of T-Cell Ontogeny

The purposes of this study were to elucidate the biologic effects of recombinant human interleukin 3 (rhIL-3) on leukemia T-cell precursors and fetal thymocytes corresponding to discrete and sequential developmental stages of human T-cell ontogeny, and to examine the biochemical nature of the IL-3 receptor linked transmembrane signal in human T-cell precursor populations. The specific binding of biosynthetically labeled 35S-rhIL-3 to leukemic T-cell precursors from T-lineage ALL patients was initially investigated. In 5 of 9 cases, the binding of 35S-rhIL-3 was significantly blocked by excess cold rhIL-3, and the percentage of inhibitable binding ranged from 40% to 64% (mean ± SE = 53 ± 4%). In these cases, 5–13 femtomols (mean + SE = 7.0 ± 1.5 fms) of 35S-rhIL-3/107 cells were specifically bound. rhIL-3 stimulated in a dose dependent fashion the in vitro clonal proliferation of leukemic T-cell precursors with composite immunophenotypes corresponding to the developmental stages of prothymocytes/double neg...