The Thymulin ELISA test principle is based on a competition between the antigen in the sample or standards and biotinylated thymulin as a tracer for the binding sites of anti-thymulin antibodies coated on the microplate wells.
A peroxidase-conjugated steptavidin is used for detection and quantification, and tetramethylbenzidine (TMB) is used as a peroxidase substrate. An acidic stop solution terminates the enzymatic reaction.
Using the values obtained from the standards, a dose-response curve of the absorbance unit (optical density, OD at 450 nm) vs. concentration is generated. This curve determines the presence of thymulin in the samples directly.