Analysis of eosinophils and myeloid progenitor responses to modified formsof MPIF-2

Myeloid progenitor inhibitory factor (MPIF)-2 is a beta -chemokine with sel ect and potent activities on eosinophils and myeloid progenitors. In the be ta -chemokine family, biological activity is modulated by differential proc essing of the amino-terminus, Here, for MPIF-2, we describe the biological activities of NH2-terminal deletion mutants and compare regions necessary f or eosinophil and myeloid progenitor activities. Five MPIF-2 proteins with deletions at the amino-terminus were produced in Escherichia coli and assay ed for calcium mobilization, chemotaxis and receptor binding activities on eosinophils, and for their ability to inhibit colony formation of human mye loid bone marrow progenitors. For eosinophils, deletion of the first two am ino acids did not markedly alter activity, while subsequent truncations res ult in a complete loss of activity. One of the MPIF-2 mutants, MPIF-2 (P30- R99) was converted from an agonist to an antagonist of eotaxin, MPIF-2 and MCP-4 functional responses in eosinophil calcium flux and chemotaxis assays . Surprisingly, while displaying a complete loss of agonist activity toward eosinophils, MPIF-2 (P30-R99) retains ability to inhibit human bone marrow myeloid progenitor cell colony formation. In addition, processing at the a mino terminus of MPIF-2 in vivo, may result in a chemokine with altered bio logical activities. (C) 2001 Academic Press.