Immunohistochemistry Introduction

Immunohistochemistry is based on the principle of antibodies binding specifically to antigens in biological tissues to detect the antigens in cells of a tissue section. It is a process used to diagnose some types of cancer including mesothelioma. The procedure involves locating antigens in biopsy tissue through the use of a visual marker. The cellular events associated with cancerous tumors will be highlighted by the stained tissue sample. Besides, immunohistochemistry can also distinguish whether or not a tumor is benign or malignant.

The principle of IHC was uncovered in the 1930s and about ten years later the first IHC study was reported. Since then, with improvement and development of protein conjugation, enzyme labels have been introduced, such as peroxidase and alkaline phosphatase. Later colloidal gold label, radioactive elements were introduced and the immunoreaction could be visualized by autoradiography. Now immunohistochemistry has become a routine and essential tool in diagnostic and research laboratories.

Immunohistochemistry (IHC) analysis

Immunohistochemistry (IHC) analysis is a method for demonstrating the presence and location of proteins in tissue sections. This method is believed less sensitive quantitatively than immunoassays such as western blotting or ELISA, but it has advantage that it enables the observation of processes in the context of intact tissue. This is especially useful for assessing the progression and treatment of diseases such as cancer.

Immunohistochemical staining is accomplished with antibodies that recognize the target protein. The antibody-antigen interaction will be visualized using either chromogenic detection or fluorescent detection.

Immunohistochemical Methods

Direct Method：Direct method is one step staining method, and involves a labeled antibody (i.e. FITC conjugated antiserum) reacting directly with the antigen in tissue sections.

Indirect Method：Indirect method involves an unlabeled primary antibody (first layer) which react with tissue antigen, and a labeled secondary antibody (second layer) react with primary antibody.

PAP Method (peroxidase anti-peroxidase method): PAP method is a further development of the indirect technique and it involves a third layer which is a rabbit antibody to peroxidase, coupled with peroxidase to make a very stable peroxidase anti-peroxidase complex.

Avidin-Biotin Complex (ABC) Method: ABC method is standard IHC method and one of widely used technique for immunhistochemical.

Labeled StreptAvidin Biotin (LSAB) Method：A recent report suggests that LSAB method is about 5 to 10 times more sensitive than standard ABC method.

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