Description
Background/Introduction: Interferon gamma (IFNgamma) is a dimerized soluble cytokine that is the only member of the type II class of interferons. The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. Wheelock as a product of human leukocytes stimulated with phytohemagglutinin, and by others as a product of antigen-stimulated lymphocytes or tuberculin-sensitized mouse peritoneal lymphocytes challenged with PPD; the resulting supernatants were shown to inhibit growth of vesicular stomatitis virus. Those reports also contained the basic observation underlying the now widely employed interferon gamma release assay used to test for tuberculosis. In humans, the IFNgamma protein is encoded by the IFNG gene. IFNgamma, or type II interferon, is a cytokine that is critical for innate and adaptive immunity against viral, some bacterial and protozoal infections. IFNgamma is an important activator of macrophages and inducer of Class II major histocompatibility complex (MHC) molecule expression. Aberrant IFNgamma expression is associated with a number of autoinflammatory and autoimmune diseases. The importance of IFNgamma in the immune system stems in part from its ability to inhibit viral replication directly, and most importantly from its immunostimulatory and immunomodulatory effects. IFNgamma is produced predominantly by natural killer (NK) and natural killer T (NKT) cells as part of the innate immune response, and by CD4 Th1 andCD8 cytotoxic T lymphocyte (CTL) effector T cells once antigen-specific immunity develops.
Principle of the Assay: This assay employs a two-site sandwich ELISA to quantitative IFN-gamma in Guinea pig serum, plasma. An antibody specific for IFN-gamma has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any IFN-gamma present is bound by the immobilized antibody. After removing any unbound substances, a biotin - conjugated antibody specific for IFN-gamma is added to the wells. After washing, Streptavidin conjugated Horseradish Peroxidase (HRP) is added to the wells. Following a wash to remove any unbound avidin-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of IFN-gamma bound in the initial step. The color development is stopped and the intensity of the color is measured