Interleukin-34 (IL-34) is a cytokine that was discovered in 2008 through functional screening of the extracellular proteome. It shares many functional similarities with colony-stimulating factor 1 (CSF-1), as both can bind to the CSF-1 receptor (CSF-1R) and regulate the differentiation and function of monocytes and macrophages. IL-34 is expressed in various tissues, including the brain, skin, and immune organs, and plays important roles in immune regulation, tissue homeostasis, and inflammation.
The IL-34/CSF-1R axis is a potential therapeutic target for various diseases, including cancer, inflammatory diseases, and autoimmune disorders. Also, IL-34 can serve as a biomarker for certain conditions. For instance, its expression levels in tissues or body fluids may indicate the presence or severity of diseases such as liver fibrosis and diabetic complications.