Natalizumab (Tysabri®) is a humanized monoclonal antibody against the cell adhesion molecule alpha4-integrin used in the treatment of multiple sclerosis and Crohn's disease. Tysabri® and was previously named|Antegren®. Natalizumab is administered by intravenous infusion every 28 days and reduces the ability of inflammatory immune cells to attach to and pass through the cell layers lining the intestines and blood–brain barrier||Sample Type:|Serum and plasma||Intended Use:|This kit is designed to measure free Natalizumab with high specificity and sensitivity in biological matrices.||Sensitivity:|1.5ng/ml ||Recovery:|250ng/mL of Natalizumab was spiked in 10 lots of human serum. Recovery ranges are from 90-108% with an average recovery of 96%.||Precision: |Intra-assay CV: <10% |Inter-assay CV: <10%. ||Specificity:|Human IgG1 and rituximab prepared at 250ng/mL were assayed and exhibited no crossreactivity or interference.||Test Principle:|This assay employs the sandwich enzyme immunoassay technique. Capture antibody is coated onto a 96 well microplate. Calibrator and test samples are pipetted into the appropriate wells. Natalizumab present in biological matrices is bound by the immobilized anti-Natalizumab|antibody. After washing away any unbound substances, enzyme linked anti-Natalizumab antibody is added to the wells. The plate is washed to remove any unbound antibody-enzyme reagent and a substrate solution is added to the wells for color development. The color development is proportional to the amount of Natalizumab present in test samples. The color development is stopped and the intensity of the color is|measured.||Kit Components:|Coated microtiter plate, 1x96 wells |Calibrator diluent, 1x1.8ml|Calibrator (0.5mg/mL), 1x12ul|Wash buffer, 10X, 1x25ml|Assay buffer 1x50ml|Detection reagent, 1000X, 1x17ul|TMB, 1x12ml|TMB stop solution, 1x12ml||Storage and Stability:|Store kit components at -20°C unless specified otherwise. Unopened kit is stable for 6 months after receipt. For maximum recovery of product, centrifuge small tubes on pulse setting prior to opening.