<P> Secondary antibodies can be conjugated to enzymes such as horseradish peroxidase (HRP) or alkaline phosphatase (AP); or fluorescent dyes such as fluorescein isothiocyanate (FITC), rhodamine derivatives, Alexa Fluor dyes; or other molecules to be used in various applications . Secondary antibodies are used in many biochemical assays including: </P> <Ul> <Li> ELISA, including many HIV tests </Li> <Li> Western blot </Li> <Li> Immunostaining </Li> <Li> Immunohistochemistry </Li> <Li> Immunocytochemistry </Li> </Ul> <Li> ELISA, including many HIV tests </Li>

Where are the origins of secondary antibodies developed