Colony stimulating factor 1(CSF-1), Also known as macrophage-colony stimulating factor, belongs to the type III protein tyrosine kinase receptor family and is expressed on macrophages, plasmacytoid, conventional dendritic cells, and osteoclasts. M-CSF is a secreted cytokine that enables hematopoietic stem cells to differentiate into macrophages or other related cell types; it also primes and enhances macrophage killing of tumor cells and microorganisms, regulates the release of cytokines and other inflammatory modulators from macrophages. M-CSF is also essential for the survival and proliferation of osteoclast progenitors.

Rhesus macaque CSF1 is engineered as a continuous single chain polypeptide in which the CSF1 (E33-G182) is linked with the Mamu Fc (LALA mutant) via a 15 amino acid linker. The 293FS cells were stably transduced with lentivirus harbouring the CSF1-Fc ORF. In 293 cells, the CSF1-Fc is expressed constitutively under the control of a CMV promoter. The resulting 387 amino acid CSF1-Fc is purified to homogeneity using protein A affinity resin. Purity is verified by SDS-PAGE.

Bioactivity of each lot is determined based on the induction of proliferation of the M-CSF dependant NFS-60 cell line. Biological activity ranges between 5.7-7.5×104 U/mg.