IGFBP1, IGFBP2, IGF2 and ANGPTL3 stimulate the ex vivo expansion of CD34+CD38−CD90+primitive progenitors at low dose. Post-thaw umbilical cord blood cells (4 × 105 cells/ml) were suspended in serum-free Stemspan® media (Stemcell technologies, vancouver, BC, Canada) supplied with different doses of indicated cytokines in the range 0 to 200 ng/ml and standard cytokine combinations of 100 ng/ml stem cell factor, 50 ng/ml FLT3 ligand and 100 ng/ml thrombopoietin, inoculated on a passage 3 to 5 bone marrow-derived mesenchymal stromal cell layer in a 24-well plate and cultured for 12 days. (A) Expansion of viable total nucleated cells (TNCs). (B) Expansion of CD34+ cells. (C) Expansion of granulocyte–macrophage colony-forming units (CFU-GM). (D) Expansion of CD34+CD38−CD90+ cells. Results expressed as mean ± standard deviation. For each novel cytokine, a t test was performed between the variant cytokine dosage group and baseline (standard cytokine combination). **P < 0.01. ANGPTL, angiopoietin-like protein; IGF, insulin-like growth factor; IGFBP, insulin-like growth factor binding protein.