Staphylococcal protein A (SPA) immunoassay technology

Staphylococcal protein A (SPA) is a protein isolated from the cell wall of Staphylococcus aureus. Due to its immunological properties, it is an extremely useful tool in immunology. The staphylococcal protein A (SPA) immunodetection technology is based on the principle that it can bind to the Fc ends of various animal IgGs. SPA markers (enzymes, fluorescein, radioactive substances, etc.) are used to show various immunity of antigen-antibody binding reactions Test experiment.

SPA has the ability to bind to human and various animals such as guinea pigs, rabbits, pigs, dogs, mice, monkeys, and other IgG. It can solve the problem of labeling the corresponding secondary antibodies separately when testing different animals. The SPA binding site is the Fc segment, and this binding will not affect the activity of the antibody. The binding force of SPA is bivalent. Each SPA molecule can simultaneously bind two IgG molecules, or it can be combined with IgG on the one hand, and on the other hand with labels such as luciferin, peroxidase, colloidal gold and iron Combination of protein and so on. However, it should be noted that SPA is selective for the binding of IgG immunoglobulin subtypes, such as SPA and human IgG subtypes: IgG 1, IgG 2 and IgG 4 have binding force, but only do not bind IgG 3. Only IgA 2 is bound, not IgA 1. SPA does not bind to poultry serum IgG. Therefore, attention should be paid to possible false negative results. SPA commonly used HRP mark, can be applied to indirect method.

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