The ImmPRESS Kit from Vector Laboratories is a new kit for immunohistochemistry (IHC) based on enzymatic detection of primary antibody using peroxidase-coupled secondary antibody. Detection techniques of primary antibody are generally based on 3 different methods: i) avidin/biotin system, ii) catalyzed signal amplification, iii) polymer-based methods. The ImmPRESS Kit is a biotin/avidin-free kit based on a new method which allows coupling a polymerized form of a reporter enzyme to secondary antibodies.
IHC is frequently used for detection of specific antigens in a tissue and is employed in pathology laboratories for diagnostic purposes or for determination of the expression pattern of a protein of interest. IHC is based on the property of antibodies to bind specific antigens; antibodies which recognized specific antigens of interest (i.e. primary antibodies) are generally detected with secondary antibodies conjugated to an enzyme or a fluorochrome (immunohistofluorescence). The secondary antibody is directed against the Fc portion of the primary antibody and is, therefore, specific to the species in which the primary antibody was raised. The relative abundance of a given antigen in a tissue, especially when working with thin sections or with low-expressed antigens, can pose challenges to detection via IHC.
One of the main focuses of our laboratory is the study of the function of transcription factors. We are working on various tissues including mammary gland, brain, colon as well as tumor samples. We have experienced difficulties working on 4-6 um paraffin sections with certain type of antigens. I have been trying various antigen retrieval and detection methods with very limited success. I then tried the ImmPRESS Kit and obtained amazing results with low background staining as compared to what we had previously obtained. We are now employing the kit for our routine IHC.
Indeed, the sensitivity of detection is far greater than other kits I used in the past. As a consequence, we are using less concentrated primary antibody and are able to complete our staining in half a day: 1 hr incubation in primary antibody dilution and 30 min incubation in ImmPRESS Reagent, instead of the 2 days previously required due to the need for overnight incubations. This is a considerable benefit in terms of time and expense.
The kit is composed of normal horse serum and secondary antibody solutions, all reagents are ready-to-use packaged in 50 ml drop dispenser bottles. No dilution or direct pipetting from the bottles is required. It is convenient and the kit is easy to use. The kit exists in mouse (Catalog No MP-7402), rabbit (Catalog No MP-7401), goat (Catalog No MP-7405) or universal (for detection of either rabbit or mouse primary antibodies; Catalog No MP-7500) versions. Another good thing about this kit is that different substrates can be used for colorimetric detection of peroxidase activity in order to achieve differential labeling of 2 different antigens in the same tissue sample. The cost of the product may be a bit prohibitive although the fact that the titer of the primary antibody can be significantly decreased will offset at least some of this cost.
Research Officer
Differentiation and Transcription Laboratory
Peter MacCallum Cancer Centre