Hemopexin (HPX aka beta-1B-glycoprotein) is a single chain, 439 amino acid 63 kDa glycoprotein that binds heme with the highest affinity of any known protein. The main function of HPX in the circulation is scavenging heme released by heme containing proteins such as hemoglobin. HPX removes harmful heme and other porphyrin groups to form the second line of defense, after haptoglobin, against hemoglobin-mediated oxidative damage during intravascular hemolysis. Plasma HPX levels can decrease upon injury and inflammation by LRP/CD91-mediated endocytosis of HPX-heme complexes by hepatocytes and macrophages. The sensitive quantitative measurement of human HPX in plasma and serum is easily performed with this 96 well strip format ELISA kit. The normal human plasma concentration of HPX is 0.4-1.5 mg/ml. The assay measures human HPX in the 0.1-100 ng/ml range. Samples giving human HPX levels above 100 ng/ml should be diluted in blocking buffer before use. A 1:1,000,000-1:4,000,0000 dilution for plasma or serum is suggested for best results. Human HPX will bind to the affinity purified capture antibody coated on the microtiter plate. After appropriate washing steps, biotin labeled anti-human HPX primary antibody binds to the captured protein. Excess primary antibody is washed away and bound antibody is reacted with streptavidin conjugated to HRP. Following an additional washing step, TMB substrate is used for color development at 450nm. Color development is proportional to the concentration of human HPX in the samples. A standard calibration curve is prepared using dilutions of purified HPX and is measured along with the test samples. All reagents and standards are provided in these ELISA kits.