Biological or Clinical Significance:
YKL-40, also known as human cartilage glycoprotein 39 (HC gp-39), is a 40 kilodalton glycoprotein first described in whey secretions of nonlactating cows. Subsequently, its production by chondrocytes, synovial cells, activated macrophages, neutrophils, and osteosarcoma cells has been reported. Though the role of YKL-40 is unknown at present, its pattern of expression and observed associations with various disease activities suggest it plays a role in tissue remodeling. It has both heparin and chitin binding domains and appears to be an auto antigen in rheumatoid arthritis.
The YKL-40 assay is a sandwich enzyme immunoassay in a micro titer stripwell format. The Fab fragment of a monoclonal anti-YKL-40 antibody conjugated to biotin binds to streptavidin on the strip and captures YKL-40 in a standard, control, or sample. A polyclonal anti-YKL-40 antibody conjugated to alkaline phosphatase binds to the captured YKL-40. Bound enzyme activity is detected with p-nitrophenyl phosphate as substrate.
Principle of Test Method: