What Is IGG Deficiency?

One of the types of mammalian antibodies (also known as immunoglobulin, Ig). Antibody-related immunity against pathogens is mainly provided by four types of this type, and it is also the only type that can pass through the placenta to provide passive immunity to the fetus.

IgG antibody

One of the types of mammalian antibodies (also known as immunoglobulin, Ig). Antibody-related immunity against pathogens is mainly provided by four types of this type, and it is also the only type that can pass through the placenta to provide passive immunity to the fetus.

Chinese name

IgG antibody

Foreign name

immunoglobulin G

Function

Activate complement, neutralize multiple

IgG antibodies ( immunglobulin G ) play a role in activating complement and neutralizing various toxins in the immune response. IgG antibodies are long-lasting and are the only antibodies that protect the fetus through the placenta during pregnancy. They also start from

1. Activate the classical pathway of complement to mediate lysolytic and cytotoxic effects;

2. mediate

Crude Extraction of Globulin

Most use ammonium sulfate salting out method or sodium sulfate salting out method. The ammonium sulfate salting out must undergo multiple precipitations, the first time using 40% saturation, the second time using 35% saturation, and the third time using 33% saturation. The gamma globulin after three extractions is basically an IgG component. The sodium sulfate method is simpler, and globulin can be precipitated with 20%. Although most of the gamma globulins after salting out belong to IgG, there are 5% of other band proteins, such as the heteroproteins in the gamma region. Because the IgG component also contains other so-called normal IgG, interference occurs. Therefore, the crude globulin extracted by the salting-out method can only be used for general experiments or antiserum with higher antibody titer.

Extraction of IgG by ion exchange chromatography

Commonly used ion exchangers are DEAE cellulose or QAE cellulose. QAE-Sephadex is the most ideal, and DE22, 32, and 52 can also be used. Take QAE-Sephadex A25 or A50 after acid treatment and equilibrate in 0.05 mol / L phosphate buffer pH7.5 8.6, drain the water, weigh the wet weight Ig into 10ml serum, and centrifuge or filter after 30min at room temperature. Remove the ion exchanger. The supernatant was treated once more in this way to obtain a relatively pure IgG, even without other miscellaneous proteins. Purification of IgG by this technology is simple and does not damage antibodies, and can be extracted in small quantities or prepared in large quantities.

Extraction of specific IgG by affinity chromatography

Cross-link Sepharose4B with purified antigen or crude antigen (if the monovalent specificity is not high), make an affinity chromatography column, wash the unbound heterozygous protein after passing the antiserum, and then use potassium thiocyanate It elutes with pure specific IgG antibody. Because potassium thiocyanate has a destructive effect on the antibody, it should be removed by dialysis in a timely manner. Purified IgG loses its protective effect due to its low content, so it should be applied in time or lyophilized and stored at 20 ° C, but neither is ideal. Adding triethanolamine or glycerol can protect it.

Preparation of F2 fragment by enzymatic hydrolysis

The point of action of pepsin on IgG is at the C-terminus (232 amino acid) of the disulfide bond connecting the two heavy chains. As a result, the two Fabs are connected by the disulfide bond, retaining the binding point of the antibody. Compared with IgG, F (ab ') 2 is characterized by the removal of the Fc segment, which avoids the role of receptors in cellular immune experiments; at the same time, it also loses the main antigenic characteristics of IgG and is not bound by anti-IgG antibodies; In indirect hemagglutination, sensitization of sheep red blood cells with F (ab ') 2 is better than with IgG.