Thrombin Activatable Fibrinolysis Inhibitor (TAFI), also known as carboxypeptidase B2 (PCB2), plasma carboxypeptidase-B (pCB), and carboxypeptidase-U (CPU), is a 401 amino acid 58 kDa plasma glycoprotein that is activated by thrombin. Activated TAFI (TAFIa) cleaves fibrin carboxy-terminal lysines reducing plasminogen and tPA binding sites resulting in downregulation of fibrinolysis. Although mice made genetically deficient for TAFI do not show a marked phenotype, change in human plasma TAFI level has been associated with many cardiovascular disorders. The sensitive quantitative measurement of total human TAFI antigen in plasma and serum is easily performed with this 96 well strip format ELISA kit. TAFI and TAFIa will be detected by the assay. The average concentration of TAFI in normal human plasma is 4.2 µg/ml. The assay measures total human TAFI in the 2-500 ng/ml range. Samples giving human TAFI levels above 500 ng/ml should be diluted in diluent before use. A 1:100 to 1:1,000 dilution for normal human plasma or serum is suggested for best results. Human TAFI will bind to the affinity purified capture antibody coated on the microtiter plate. After appropriate washing steps, horseradish peroxidase labeled polyclonal anti-human TAFI primary antibody binds to the captured protein. Excess primary antibody is washed away and TMB substrate is used for color development at 450nm. A standard calibration curve is prepared along with the samples to be measured using dilutions of human TAFI. Color development is proportional to the concentration of total TAFI antigen in the samples. All reagents and standards are provided in these ELISA kits.