A new lectin in red kidney beans called PvFRIL stimulates proliferation ofNIH 3T3 cells expressing the Flt3 receptor

A new legume lectin has been identified by its ability to specifically stim ulate proliferation of NIH 3T3 fibroblasts expressing the Flt3 tyrosine kin ase receptor. The lectin was isolated from conditioned medium harvested fro m human peripheral blood mononuclear cells activated to secrete cytokines b y a crude red kidney bean extract containing phytohemagglutinin (PHA). Untr ansfected 3T3 cells and 3T3 cells transfected with the related Fms tyrosine kinase receptor do not respond to this lectin, which we called PvFRIL (Pha seolus vulgaris Flt3 receptor-interacting lectin). When tested on cord bloo d mononuclear cells enriched for Flt3-expressing progenitors, purified PvFR IL fractions maintained a small population of cells that continued to expre ss CD34 after 2 weeks in suspension cultures containing IL3. These cultures did not show the effects of IL3's strong induction of proliferation and di fferentiation (high cell number and exhausted medium); instead, low cell nu mber at the end of the culture period resulted in persistence of cells in t he context of cell death. These observations led to the hypothesis that PvF RIL acts in a dominant manner to preserve progenitor viability and prevent proliferation and differentiation. (C) 2000 Elsevier Science B.V. All right s reserved.