Abstract Colony-stimulating factor-1 (CSF-1), the principal growth factor for macrophages, is
increased in the kidney, serum, and urine of patients with lupus nephritis, and eliminating
CSF-1 suppresses lupus in MRL-Fas lpr mice. CSF-1 has three biologically active isoforms:
a membrane-spanning cell surface glycoprotein (csCSF-1), a secreted proteoglycan (spCSF-
1), and a secreted glycoprotein (sgCSF-1); the role of each isoform in the circulation and
kidney in autoimmune disease is not well understood. Here, we constructed mutant MRL …