Introduction
Interferon-ɣ (IFN-ɣ) is a highly pleiotropic protein secreted mainly by activated T-lymphocytes and natural killer cells. It is involved in a wide range of physiological processes, including antiviral, immunoregulatory and anti-tumour properties, cell proliferation and apoptosis, as well as the stimulation and repression of a variety of genes (1-3). IFN-ɣ is a homodimer consisting of two 143-amino-acid polypeptides with 20 kDa and 25 kDa (4). By binding to the receptors IFNGR1 & IFNGR2, IFN-ɣ activates the tyrosine kinase JAK-STAT pathway (5). While protecting against tumor development and cancer immunoediting, IFN-ɣ function is significant in tumor surveillance (6). Aside from functions in host defense, IFN-ɣ may contribute to autoimmune pathology. In humans, IFN-ɣ is implicated in pathology of diseases such as systemic lupus erythematosus (7), multiple sclerosis (8), and insulin-dependent diabetes mellitus (9). Therapeutically, IFN-ɣ administration enhances bone resorption and leukocyte function in patients with osteopetrosis (10).

Principle of the Assay
The AssayMax Human Interferon-ɣ ELISA (Enzyme-Linked Immunosorbent Assay) kit is designed for detection of human IFN-ɣ in plasma, serum, and cell culture samples. This assay employs a quantitative sandwich enzyme immunoassay technique that measures human IFN-ɣ in less than 5 hours. A polyclonal antibody specific for human IFN-ɣ has been pre-coated onto a 96-well microplate with removable strips. IFN-ɣ in standards and samples is sandwiched by the immobilized antibody and biotinylated polyclonal antibody specific for IFN-ɣ, which is recognized by a streptavidin-peroxidase conjugate. All unbound material is then washed away and a peroxidase enzyme substrate is added. The color development is stopped and the intensity of the color is measured.