Isolation and synthesis of a hemoregulatory peptide.

A peptide was isolated in pure form from human leukocytes which strongly inhibits the proliferation of immature myeloid cells in vitro (committed stem cells). Structural investigations yielded pGlu-Asp or Glu-Asp or Glu-Cys-Lys-OH as the probable sequence of this peptide. The Glu2, Asp3-analog, prepared synthetically, displayed similar activities and when applied in vivo showed effects on the hemopoietic system ranging from an inhibition of pluripotent and committed stem cells to variations in the bone marrow proliferation and alterations in peripheral blood counts.