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From the * Department of Cell Biology, Two novel human
Department of Protein Therapeutics, and § Department of
Protein Expression and Purification, Human Genome Sciences, Inc., Rockville, Maryland 20850
-chemokines, Ck
-8 or myeloid progenitor inhibitory factor 1 (MPIF-1), and
Ck
-6 or MPIF-2, were discovered as part of a large scale cDNA sequencing effort. The
MPIF-1 and MPIF-2 cDNAs were isolated from aortic endothelium and activated monocyte
libraries, respectively. Both of the cDNAs were cloned into a baculovirus vector and expressed
in insect cells. The mature recombinant MPIF-1 protein consists of 99 amino acids and is most homologous to macrophage inflammatory protein (MIP)-1
, showing 51% identity. It displays
chemotactic activity on resting T lymphocytes and monocytes, a minimal but significant activity on neutrophils, and is negative on activated T lymphocytes. MPIF-1 is also a potent suppressor of bone marrow low proliferative potential colony-forming cells, a committed progenitor that gives rise to granulocyte and monocyte lineages. The mature recombinant MPIF-2 has
93 amino acid residues and shows 39 and 42% identity with monocyte chemoattractant protein
(MCP)-3 and MIP-1
, respectively. It displays chemotactic activity on resting T lymphocytes,
a minimal activity on neutrophils, and is negative on monocytes and activated T lymphocytes.
On eosinophils, MPIF-2 produces a transient rise of cytosolic Ca2+ and uses the receptor for
eotaxin and MCP-4. In hematopoietic assays, MPIF-2 strongly suppressed the colony formation by the high proliferative potential colony-forming cell (HPP-CFC), which represents a
multipotential hematopoietic progenitor.
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