Adjuvant

An adjuvant, also known as an immunoadjuvant, refers to all substances that are injected or pre-injected with an antigen to increase the body's immune response to the antigen or to change the type of response. The role of immune adjuvant: 1 can make weak antigenic substances enhance antigenicity; 2 increase the level of specific circulating antibodies, or produce effective protective immunity; 3 change the type of circulating antibodies produced; 4 enhance cell-mediated hypersensitivity Ability; 5 protects antigens (especially DNA, RNA) from the decomposition of enzymes in the body. Adjuvants can enhance the specific reaction of certain polysaccharides or polypeptides with low molecular weight and weak antigenicity. BCG, bacterial endotoxin, and pertussis have adjuvant effects. Adjuvants are mixed with certain tissue antigens and are susceptible to allergic reactions and autoimmune diseases. The commonly used adjuvant in the laboratory is Freund's adjuvant, which can be divided into: 1 incomplete Freund's adjuvant, which is made by mixing 1 to 6 parts of paraffin oil and 1 part of lanolin; 2 complete Freund's adjuvant, In incomplete Freund's adjuvant, inactivated BCG (2-20 mg/ml) was added before use. In the first injection of an antigen in an experimental animal, the antigen used is usually mixed with complete Freund's adjuvant, and when it is reintensified later, it is only necessary to mix with incomplete Freund's adjuvant. The adjuvant is mixed with the antigen in a ratio of 1:1, and is fully emulsified until the oil and water are separated after standing to be used for injecting the animal. [Effect of adjuvant on antigen] 1 Increase the surface area of the antigen. Adjuvant adsorption of the antigen increases the surface area of the antigen and alters the configuration of the active gene, thereby enhancing the immunogenicity of the antigen. For small molecular weight soluble antigens or haptens, after adsorption by colloidal particles, antibody production can be increased. 2 Enhance the synergy of T and B cells. Adjuvants and antigens are engulfed by macrophages, processing antigens, conferring strong immunogenicity, promoting T lymphocyte immunity, and enhancing the synergistic effect of T lymphocytes and B lymphocytes. 3 prolonging the storage time of the antigen in the tissue causes the antigen to degrade and release slowly. The adjuvant can cause local granuloma, prolong the storage time of the antigen in the local tissue, slow down the degradation rate of the antigen, and slowly release the antigen. For example, the phenomenon of retention caused by Corynebacterium parvum is much longer than that of soluble antigen. The former can last for several weeks, while the latter is only two to three days. Local inoculation of this bacterium can cause granuloma, but does not develop into epithelioid cells and multinucleated giant cells, and does not cause local tissue necrosis. After the aluminum hydroxide gel is mixed with the antigen, the antigen is adsorbed on the surface of the aluminum gel, which can prolong the time of the antigen in the body, slowly release the antigen, increase the concentration of the antibody in the blood, and reduce the number of immunizations. [The effect of adjuvant on the body] 1 Causes cell infiltration. Adjuvant can cause cell infiltration, and macrophage, lymphocyte and plasma cells can accumulate, promote the proliferation of these cells, and play a greater role. For example, after injection of FCA, it can be seen from the tissue section that the injection has local macrophages, epithelioid cells, and lymphocytes and plasma cells aggregated. 2 accelerate the transformation of lymphocytes. Adjuvants can accelerate the transformation of lymphocytes into effector cells, produce more sensitized lymphocytes and transform into plasma cells to produce antibodies. 3 membrane and cytoplasmic changes. When the lymphocytes are stimulated by the ligand, the phospholipids on the membrane are activated by the enzyme, causing membrane movement on the membrane or adjacent sites and synthesizing a new membrane. Corresponding changes also occur in the cytoplasm and nucleus, and the elevation of intracellular AMP and GMP concentrations plays an important regulatory role and influence. Similar changes were observed in macrophages after adjuvant treatment, mainly due to increased membrane activity and secretion of helper factors. 4 changes in cell function. After macrophages are stimulated and activated by adjuvants, major changes occur, including increased numbers, increased membrane surface area, and a large number of cofactors and prostaglandins. After T and B cells are treated with adjuvants, the biggest change is the increase in the number of cells, the entry into the cell proliferation cycle, and changes in the surface composition of the membrane, resulting in a large number of cofactors (LK). B cells differentiate into plasma cells and secrete large amounts of antibodies. [Mineral Oil Adjuvant] Mineral oil adjuvant is an emulsion type vaccine which is emulsified by mixing light mineral oil (trade name white oil) in accordance with medicinal standards, adding emulsifier and mixing with an appropriate ratio of aqueous antigen. An "emulsion" is a dispersion formed by dispersing a solution into fine particles and suspending it in another immiscible liquid. The dispersed material is called the dispersed phase (internal phase), the liquid that is subjected to the dispersed phase is called the continuous phase (external phase), and the interfacial active between the two phases is called the emulsifier. When water is used as the dispersed phase and the oil with emulsifier is used as the continuous phase, the emulsion prepared is a water-in-oil emulsion (water/oil type or W/O type), and vice versa is an oil-in-water emulsion (oil) / water type or O/W type). The W/O emulsion vaccine adjuvant has higher activity, but the trait is more viscous, and it is not easy to be dispersed in the animal body. Although the properties of the O/W emulsion are relatively thin, the adjuvant activity is very low. For this purpose, the W/O emulsion vaccine can be stirred with 2% Tween-80 physiological saline to form a biphasic emulsion type, that is, a water-oil-water type or a multi-type emulsion. The biphasic emulsion vaccine has a low viscosity, is easy to disperse after injection, has a slight local reaction, and has an excellent adjuvant effect.