This ELISA kit for the detection of Human IFN Gamma is a sandwich-type of enzyme immunoassay in which a monoclonal antibody has been precoated to polystyrene microtiter wells. The target is bound by the antibody on the microtiter plate. Non-bound material is then removed by washing. Subsequently, a biotinylated antibody is added. This antibody binds to the cytokine-antibody complex present in the microtiter well. Excess biotinylated antibody is removed by washing, followed by addition of horseradish peroxidase (HRP) conjugated streptavidine, which binds onto the biotinylated side of the cytokine sandwich. After removal of non bound HRP conjugate by washing, substrate solution is added to the wells. A coloured product is formed in proportion to the amount of cytokine present in the sample or standard. After the reaction has been terminated by the addition of a stop solution, absorbance is measured in a microtiter plate reader. From the absorbance of samples and those of a standard curve, the concentration of cytokine can be determined by interpolation with the standard curve.