KSP37 is a 223 amino acid protein that is secreted into the extracellular space and belongs to the fibroblast growth factor-binding protein family. Expressed in serum, as well as in cytotoxic T lymphocytes and peripheral leukocytes, KSP37 is thought to be involved in lymphocyte-mediated immunity, possibly playing a role in the development of asthma. The gene encoding KSP37 maps to human chromosome 4, which encodes nearly 6% of the human genome and has the largest gene deserts (regions of the genome with no protein encoding genes) of all of the human chromosomes. Defects in some of the genes located on chromosome 4 are associated with Huntington's disease, Ellis-van Creveld syndrome, methylmalonic acidemia and polycystic kidney disease.