RAPID COMMUNICATION Engagement of Interleukin-7 Receptor Stimulates Tyrosine Phosphorylation, Phosphoinositide Turnover, and Clonal Proliferation of Human T-Lineage

The purposes of this study were t o examine the biologic effects of the engagement of the interleukin-7 receptor (IL-7R) with recombinant human interleukin-7 (rhlL-7) in immunophenotypically distinct T-lineage acute lymphoblastic leukemia (ALL) blasts and t o elucidate the biochemical nature of the IL-7R-linked transmembrane signal in rhlL-7responsive T-lineage ALL blast populations. In the absence of costimulants, rhlL-7 stimulated the in vitro proliferation and colony formation of freshly isolated leukemic blasts from six t o eight T-lineage ALL patients with a mean plating efficiency of 196 -+ 53 (background subtracted) colonies/105 blasts plated. Stimulation of T-lineage ALL blasts with rhlL-7 resulted in markedly enhanced tyrosine phosphorylation of six distinct phosphoproteins with molecular weights of 57, 72, 98,123,150, and 190 Kd, and induced a rapid increase in the production of inositol-1,4,5-trisphosphate ( lns-1,4,5-P3). which