L-17 has recently been of great interest in immunological research. It is generally regarded as a mediator of communication between the immune system and the hematopoietic system. Originally known as cytotoxic T lymphocyte-associated antigen-8 (CTLA-8), IL-17 is naturally found as a disulfide-linked homodimer of a 155 amino acid sometimes glycosylated polypeptide. The receptor appears to be related to class I cytokine receptors and is expressed on mast cells, fibroblasts, fetal hepaocytes, pre-B cells and intestinal epithelial cells.

The hemotopoietic effects of IL-17 are evidenced by the IL-17 induced fibroblast production of IL-6, IL-8, ICAM-1 and G-CSF. These promote granulocyte, macrophage, and neutrophil development, while IL-17 directly enhances proliferation of activated T cells and upregulates nitric oxide production in osteoarthritic cartilage.

IL-17 is often assayed in conjunction with IL-15, IL-23, and other effectors of hematopoesis such as EPO, IL-3, IL-5, IL-6, TPO, G-CSF, and GM-CSF.