1 Definition Editing is the main component of serum immunoglobulin, accounting for 75% of the total content of immunoglobulin in serum, and the normal value is 9.5~12.5mg/ml. 40-50% of them are distributed in serum, and the rest are distributed in tissues. The molecular weight is about 150,000 Daltons. The IgG in human serum is mainly a monomer, and the normal human IgG includes four subtypes, IgG1 accounts for 60-70%, IgG2 accounts for 15-20%, IgG3 accounts for 5-10%, and IgG4 accounts for 1-7%. These subtypes have different binding abilities on the classic pathway of complement activation. IgG is mainly synthesized by plasma cells in the spleen and lymph nodes. It is the only antibody that can pass through the placenta and plays a major role in preventing infections within a few weeks of birth. The baby has been able to synthesize IgG in the third month after birth, and has reached the human level at the age of 2 to 3. After the age of 40, it gradually declined. The content of IgG varies greatly from person to person, and the same individual fluctuates greatly under different conditions. Most of the antibacterial, antiviral, and antitoxin antibodies produced by the body under antigenic stimulation are IgG. Many autoantibodies, such as the LE factor of systemic lupus erythematosus, and anti-thyroglobulin antibodies are also IgG. IgG is the main antibody against immunity in the body. Immunoglobulin G immunoglobulin G A group of globulins with special chemical structures and immune functions, present in body fluids and on the surface of lymphocytes, is the material basis of antibodies. They are divided into five categories according to their structure and function: IgG, IgM, IgA, IgD and IgE. Its molecular size, charge, amino acid composition and carbohydrate content are very heterogeneous. When suffering from allergic diseases, autoimmune diseases, various infections, and multiple myeloma, immunoglobulins can be abnormally increased. Immunoglobulins can be abnormally reduced in patients with immunodeficiency syndrome such as acquired immunodeficiency syndrome. Immunoglobulin preparations are often used clinically to prevent infectious diseases, certain tumors and immunodeficiency diseases. 2 Basic structure editing The basic structure of the Ig molecule is symmetric four polypeptide chains, that is, two identical light chains (L chains) and two identical heavy chains (H chains), which are linked by interchain disulfide bonds. "Type monomer molecules (Figure 1). Different classes of Ig molecules are determined by the structure of their respective heavy chains. The heavy chain is divided into five categories: γ, μ, α, δ and ε chain, and can be divided into several subclasses according to the antigenicity of the heavy chain. The light chains of the five types of Ig molecules are the same, and can be divided into κ type and λ type, and the amino acid and antigenicity of the two types are not the same. The amino acid sequences at the amino terminus of the light and heavy chains are subject to change, so this portion is referred to as the variable region (V region). The V region is a site for identifying an antigen and determining the specificity of the antibody. The number and order of amino acids in the rest of the peptide chain (ie, the carboxy terminus) are relatively constant, so it is called the stable region (C region). The stable zone determines the various biological functions of the Ig molecule. The main biochemical properties of Ig are shown in Table 1. The papain can be used to break the immunoglobulin into three fragments of similar size. Two of the fragments can bind to the antigen, called the antigen-binding fragment (Fab segment), and the other fragment can be crystallized, called the crystalline fragment (Fc segment). The immunoglobulin can be broken into two segments by gastric enzyme. One large fragment is 5S duplex F(ab')2, and a small fragment is similar to Fc, which is called pFc' (Fig. 2). Types of Immunoglobulin (Ig) Molecules Ig Molecules have different variability due to different genetically controlled antigenicities, ie, specific antigenic determinants. Includes: 1 homologous specificity. An antigenic marker possessed by all Ig molecules of all members of the same genus. For example, all humans have five types of immunoglobulins, of which IgG can be divided into four subclasses of IgG1 to IgG4 according to different heavy chain amino acids; IgM has two subclasses of IgM1 to IgM2, and IgA has two subclasses of IgA1 to IgA2. IgD has two subclasses, IgD1 to IgD2. 2 heterotypic specificity. Ig molecules of the same genus different members may have specific antigenic markers that are not identical. 3 unique type (Id). Each Ig molecule can have a unique antigenic determinant. Since there are millions of antibody-forming cell clones (cell lines) in the body, it is conceivable that there are a large number of unique types. 3 Biological function editing Ig molecules have the dual function of binding antigen and stimulating antibody production (Table 2). First, it can bind to antigens and produce a variety of biological effects, including: 1 binding to pathogenic microorganisms or toxins secreted by it, producing anti-infective immunity; 2 activating normal components of body fluids, ie, complement molecules, acting as killing pathogens Or the role of target cells; 3 to enhance the phagocytic or killing effect of immune cells such as phagocytic cells; 4 combined with mast cells or basophils in the tissue to produce an allergic reaction; 5 to close the transplanted organs, enhance its protection , slow rejection; 6 closed tumor cells, reducing immune protection. The immunoglobulin can also be delivered to the fetus through the placenta. In addition, since the Ig molecule is composed of a glycoprotein, in addition to the above antibody activity, there is antigenicity, and the autoimmune cell can be activated to produce an antibody against the antibody, an anti-idiotypic antibody (Id antibody), thereby forming a self-regulating Features. Characteristics of various immunoglobulins Five types of Ig have different physical and chemical properties. 1 IgG. IgG is the main Ig in biological fluids, accounting for about 70 to 75% of the total amount of Ig in the blood. Since IgG can pass through the placenta, IgG obtained from the mother by newborns plays an important role in fighting infection. The babies begin to synthesize IgG 2 to 4 weeks after birth, and the serum IgG can reach adult levels after 8 years of age. Because IgG spreads more easily into the extravascular space than other types of Ig, it plays an important role in binding complement, enhancing the ability of immune cells to phagocytose pathogenic microorganisms and neutralizing bacterial toxins, and is effective against infection, which is beneficial to the human body. Side. However, autoimmune diseases such as autoimmune hemolytic anemia, thrombocytopenic purpura, lupus erythematosus, and rheumatoid arthritis are all IgG. Once it binds to the corresponding autologous cells, it strengthens the tissue damage. 2 IgM. IgM has the largest molecular weight in Ig, commonly referred to as macroglobulin, which accounts for 10% of the total serum Ig. Observed under an electron Microscope, IgM consists of five monomers of the same basic structure. Each unit is connected by a connecting chain (J chain) into a "star" pentamer. IgM is the earliest antibody produced during the development of the individual, and is also the first antibody in the antigen-stimulated animal. Therefore, checking the content of IgM is helpful for the early diagnosis of infectious diseases. IgM begins to synthesize 3 months after the fetus, but the level is very low, and the serum IgM content reaches adult level at 1 to 2 years of age. By binding to complement, IgM has the effect of dissolving bacteria and dissolving blood cells, and neutralizes the virus, which is 100 times more potent than IgG. Many anti-microbial natural antibodies, homologous hemagglutinin (anti-A and anti-B blood), rheumatoid factor in rheumatoid disease, and complement-binding antibodies to syphilis belong to IgM. 3 IgA. The content of IgA in serum is second only to IgG, accounting for 10-20% of the total serum Ig. IgA has a different form such as a monomer (1 basic structure), a double body (2 basic structures) or a multimer (several basic structures linked by a J chain). The serum is serotype IgA, mainly 7S monomer. IgA in various secretions such as saliva, tears, sweat, colostrum, respiratory tract and digestive tract secretions is secretory IgA (SIgA) composed of dimers and multimers, in addition to secretory bodies. Secretion bodies help secretory IgA to resist hydrolysis of the protease and cause IgA to enter the secretion through the mucosa of the secretory tissue. Secretory IgA has a clear protective surface and protects against pathogen invasion. 4 IgD. IgD is very low in serum (less than 1% of the total). IgD is more susceptible to hydrolysis by proteolytic enzymes than IgG1, IgG2, IgA or IgM and is readily autolyzable. The biological function of IgD is not well understood. Currently known IgD antibody activities include anti-nuclear antibodies, anti-base membrane antibodies, anti-insulin antibodies, anti-streptolysin O antibodies, anti-penicillin antibodies, and anti-toxins against diphtheria toxin. Little is known about the relationship between IgD and disease. 5 IgE. The serum IgE content in normal serum is extremely low. IgE is mainly synthesized by plasma cells in the respiratory and intestinal lymph nodes. Secretory IgE is present in the nasal cavity, bronchial secretions, milk and urine. IgE is a pro-cell antibody that binds to mast cells in basophils or tissues of blood and vascular endothelial cells. When various allergens such as pollen are encountered, antigens and IgE bind to these cell surfaces. It releases a large amount of active medium, such as histamine, and the like, and induces type I allergic reaction. 4 Antibody Diversity Editing antibodies can produce millions of different immunoglobulin molecules, and almost all antigens that enter the body can react specifically with the corresponding antibodies. There are six theories that explain the genetic material that encodes such a large number of antibodies, that is, genes. 1 embryology theory. The early view was that when you were born, there were all the genes that were fully equipped to encode antibody molecules, which were inherited through germ cells. It was subsequently found that each lymphocyte had the genetic information of the Ig molecule, so that the VL and VH gene products provided sites for binding to various antigens, and the relationship between the parental gene of the Ig gene and the progeny was ensured. The diversity of V, D, and J fragments in the daughter cell genes. 2 Somatic mutation theory. It is believed that each germ cell does not have all the genetic information that forms the Ig molecule, and it inherits only a few V-region genes. However, during somatic development, the V gene produces diversity due to somatic mutations. To this end, each immune cell can express different specificities. 3 Free combination theory. The Ig variable region (V region) is divided into a V segment, a D segment, and a J segment. These genes are freely combined to form a light chain with a VJ code and a heavy chain with a VDJ code. Further, it can be combined into a plurality of V regions having light and heavy chains. The V region gene is then combined with a different C gene to form a complete light and heavy chain gene. The genes of the light and heavy chains can be recombined into more Ig genes. 4 Connection diversity theory. The nucleotide of the 96th amino acid in the third variable region encoding the kappa light chain can be diverse due to the order in which the V and J fragments bind. This diversity of connection sequences also exists in the heavy chain. 5 Diversity of D gene translation in multiple frameworks. When the D gene encodes Ig diversity, it is translated according to three frameworks. The first is the most appropriate frame, followed by the forward frame or the backward frame. Each translational form can direct the order in which a D fragment is translated into multiple amino acids. It depends on which form a B cell takes, depending on the specificity of the antibody produced. 6 Small gene insertion theory. During the ligation of the D segment and the J segment, the V region base pair can be inserted into the minigene to produce a highly variable region. In a nutshell, under certain conditions, after the antigen activates B cells, plasma cells are formed, and under the VDJ code, Ig molecules containing different amino acid sequences and different spatial configurations are secreted. That is, for ever-changing antigens, antibodies can produce corresponding antibodies with different antigen-binding sites, resulting in a variety of immune responses. Elisa kit, elisa kit, Shanghai elisa test, SOD kit, IgG kit, IgM kit, WB test, immunohistochemistry, radioimmunoassay, GIBCO, AMRESCO-Shanghai Xinfan
Medical students can use this model to practice. Doctors can explain the extraction to patients. In addition, the model can also be used for exhibition and other purposes. The human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food, the canines tear the food and the molars and premolars crush the food. The roots of teeth are embedded in the maxilla (upper jaw) or the mandible (lower jaw) and are covered by gums. Teeth are made of multiple tissues of varying density and hardness.
Dental Model,Teeth Model,Dental Teeth Model,Dental Study Models
Xinxiang Vic Science&Education Co.,Ltd. , https://www.labmedicalscience.com