A Sandwich ELISA for Detection of Soluble GPI-80, a Glycosylphosphatidyl-Inositol (GPI)-Anchored Protein on Human Leukocytes Involved in Regulation of Neutrophil Adherence and Migration-Its Release from Activated Neutrophils and Presence in Synovial Fluid of Rheumatoid Arthritis Patients

GPI‐80, mainly distributed on human neutrophils and monocytes, is a novel glycosylphosphatidylinositol (GPI)‐anchored protein regulating neutrophil adherence and migration. We prepared a polyclonal antibody specific to GPI‐80 by immunizing rabbits with the purified GPI‐80 and established a sandwich ELISA for detecting soluble GPI‐80. We found that soluble GPI‐80 was released from fMLP activated neutrophils and was present at high concentrations in synovial fluids but not sera of rheumatoid arthritis patients, suggesting that GPI‐80 may play a role in inflammatory diseases. The detection of soluble GPI‐80 may help us to understand its physiological and pathological functions.