The identification of the HYAL1 hyaluronidase enzyme as a human plasma-derived myeloid colony-stimulating factor (CSF), herein designated CSF5-hyaluronidase, its recombinant production and methods of use are described. This protein may be used for the treatment of myelosuppression as may occur after irradiation, chemotherapy or other diseases where an increase in leukocyte levels may be beneficial. For example, CSF5- may be used to enhance the immune response to viral infection or other diseases associated with immune suppression.