Mammalian antibodies are often used for IVD applications. But the problem with these antibodies is that the Fc domain leads to cross-reactions with Fc receptors. The Fc receptors belong to a family of cell surface molecules that are present on almost every cell of the immune system.

If mouse antibodies are used for diagnostic applications, it can also happen that they are bound by non-specific human anti-mouse antibodies or rheumatoid factors. Because of this interaction, it can happen that a patient can also undergo diagnostic tests, or he even gets a misdiagnosis. Therefore, an antibody that can avoid cross-reactions by the Fc domain has a huge benefit.

IgY is the functional, equal and evolutionary precursor of immunoglobulin G (IgG) of mammals. This protein is found in birds, reptiles and amphibians. Ducks have in addition a reduced version of the IgY protein, which lacks the Fc domain: IgY ("Fc).

IgY antibodies have a very big impact ability, but are still not widespread in the industry, although an egg is a unique bioreactor for the production of antibodies. Moreover, the production is easier and more animal-friendly than those from mammalian serum.

If ducks are vaccinated with an antigen, the thereby resulting antibody is given also to the yolk. Because IgY antibodies are difficult to isolate from egg yolk, it ist rarely used. However, recently a method was developed, how to isolate antibodies from duck egg yolk.

You get the main part of the IgY ("Fc) antibodies with a purity of 95%, through a process with delipidation, salting, desalting and concentration. This way of production is very cheap because adult ducks lay about 250 eggs a year. From this egg yolk you can isolate 75-120 mg of antibody each.

The separated IgY ("Fc) have shown a greater inclination to mammalian albumin in analysis than the corresponding rabbit antibodies. This high level of recognition and binding specificity could be due to the phylogenetic differences between the proteins of birds and mammals. These are obviously larger than that of mammal to mammal. Because of these characteristics, the bird antibodies are especially suitable for immunological studies on mammalian species that affect the immune system. Other tests have shown that not only goat IgG, rabbit IgG, and duck IgY ("Fc) remain stable if they were treated for 4 hours at pH values of 3.5 to 9. Were the pH values below 3.5 or over 10, all antibodies have lost with time the ability to create antigen-antibody complexes. In these exceptional circumstances, the goat IgG was the weakest and the rabbit IgG most resistant. Likewise, all three antibodies acquitted in a thermal stability test. In this, the antibodies were stored 80 days with a temperature of 40 ° C. There was no evidence for a cross-reactivity between duck IgY ("Fc) and mammalian antibodies. IgY ("Fc) is suitable for IVD applications. This suggested a LIT-test (latex-enhanced Immunoturbidimetric test).

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