Macrophage-Inflammatory Protein-3β/EBI1-Ligand Chemokine/CKβ-11, a CC Chemokine, Is a Chemoattractant with a Specificity for Macrophage Progenitors Among Myeloid Progenitor Cells

Chemoattractants are potential factors influencing cell migration. Stromal cell-derived factor-1, a CXC chemokine, is the only chemokine reported to have chemotactic activity for hemopoietic progenitor cells (HPC). We report in this work another chemokine of the CC subfamily, which is chemotactic for HPC. Macrophage-inflammatory protein (MIP)-3β/EBI1-ligand chemokine/CKβ-11 attracted bone marrow and cord blood CD34+ cells. In contrast to stromal cell-derived factor-1, which attracts multiple types of HPC, MIP-3β attracted mainly CFU granulocyte macrophage, but not other HPC such as burst-forming unit erythrocyte or CFU granulocyte, erythrocyte, macrophage, and megakaryocyte. Chemoattracted CD34+ cells formed CFU granulocyte macrophage-like colonies, which were morphologically determined as large macrophages. These progenitors were selectively responsive to stimulation by macrophage CSF, demonstrating that MIP-3β attracts macrophage progenitors. Expression of CCR7, the receptor for MIP-3β, was detected at a mRNA level in the attracted CD34+ cells as well as input CD34+HPC. Expression of MIP-3β mRNA was not constitutive, but was inducible in bone marrow stromal cells by inflammatory agents such as bacterial LPS, IFN-γ, and TNF-α. Taken together, our findings suggest that MIP-3β is expressed in the bone marrow environment after induction with certain inflammatory cytokines and LPS, and may play a role in trafficking of macrophage progenitors in and out of the bone marrow in inflammatory conditions.