The body's specific immune response
When the foreign antigen material enters the body, the body's specific immune response is the process of cellular immunity and humoral immunity stimulated by the antigen material. After a certain amount of antigen material enters the body, how can specific immune reactions (including cellular immunity and humoral immunity) occur in the body's immune organs and immune cells to produce specific antibodies?
After the antigen enters the body for the first time, it is immediately engulfed by macrophages, most of which are broken down into immune fragments, and then combined with the macrophage mRNA to form a complex, which is released from the phagocytes. This antigen processed by phagocytic cells stimulates T cells and B cells to make most of them transformed into lymphoblasts and plasmablasts respectively, thereby producing more sensitized lymphocytes and plasma cells, some of which are affected by antigens. After stimulating, it stops differentiation and becomes memory cells. These memory cells can also have a secondary immune response with the same antigen that re-enters the body for months or even years after the antigen stimulation is terminated.
After being stimulated by antigens, T cells are transformed into lymphoblasts and sensitized lymphocytes, and the same antigens are confirmed again, which can produce various lymphokines such as macrophage migration inhibitory factor, macrophage arming factor and lymphotoxin. Form a cellular immune response.
After being stimulated by the antigen, B cells proliferate and differentiate into plasmablasts and plasma cells, produce and secrete specific antibodies (immunoglobulins), and form a humoral immune response.
Of course, after the antigen enters the body, only a part of it functions with the body's immune active cells, and part of it is excluded by the body's metabolic organs.
There are many ways for an antigen to react with lymphocytes to produce an immune response: antigens can first interact with macrophages and then pass to lymphocytes, or they can directly interact with lymphocytes (including T cells and B cells) to produce an immune response. After the antigen substance stimulates the body, there is a certain pattern of antibody production. That is, after the antigen enters the body, it first passes a period of incubation, and then the antibody content gradually increases. After reaching the peak, it is temporarily maintained for a certain period of time, after which the antibody content gradually decreases and the initial Stages of reaction. When the same antigen is re-stimulated for the second time, the antibody content rises faster than the initial response, and the peak value is higher than the previous time, and the peak duration is also longer, forming a re-reaction phase.
If the antibody content is the highest, you can usually get highly effective antiserum. After blood collection, if the same antigen is not injected, the body's ability to produce antibodies will gradually decline. However, if the animal rests for a long time, such as 2 ï¼After 3 months, if the same small amount of antigen is injected again, its antibody content will rise quickly, and high-potency antiserum can be obtained again. The body's specific immune response is directly related to the formation of antibodies. Therefore, it is particularly important to pay attention to the factors that affect the body's antibody production under antigen stimulation.
Special attention should be paid to the selection of suitable animals. To immunize animals, age, weight and gender should be considered. Animals used for immunization are too young, and the immune system is not yet fully developed, which will affect the formation of antibodies; too old, because of the weakening of metabolic function, will also affect the formation of antibodies. Therefore, for the rabbits commonly used in the laboratory, it is best to choose a healthy male white rabbit with a rabbit age of 9-24 months, a weight of 2-2.5 kg, large ears, thick veins, and no ringworm.
Use the appropriate antigen dose. Too much antigen dose will cause immune paralysis; too small will not stimulate the body's reaction, and the immune paralysis caused by multiple low-dose injections is much more serious than the immune paralysis caused by a large dose, which is not conducive to antibodies form. For the response of antigen to stimulate B cells, in order for B cells to produce a large amount of antibodies, it is necessary to inject a suitable dose of antigen.
Pick the appropriate injection route and site. There are many ways for antigens to enter the body, such as muscle, intradermal, subcutaneous, lymph nodes, veins, soles, and abdominal cavity. There are two commonly used routes: one intramuscular injection and the other is intravenous injection. If the two routes are used alternately, then intravenous injection should be followed by intramuscular injection. For a certain route, for example, intramuscular injection, multiple injections are often made in different muscle parts, and the immune effect is also better. The way of injection is related to the nature of the antigen. For some viruses, such as turnip mosaic virus, it is not suitable for intravenous injection because of the addition of many chemicals during purification. In addition, in order to prevent animals from getting angry at the injection point, the dosage of each injection point should not be greater than 0.5ml.
Supplemented by a suitable adjuvant. In order to slowly release the antigen in the body and prolong the residence time of the antigen in the body, so that the initial reaction and the second reaction of the antibody are combined, an adjuvant is often added to the antigen and mixed with the antigen and injected together. Inside the animal. Commonly used adjuvants are: Freunds adjuvant and alum adjuvant. Freund's adjuvant is a mixture of paraffin oil and lanolin, and their ratio depends on the situation. Freund's adjuvant is divided into complete and incomplete. The so-called complete Freund's adjuvant is to add heat-inactivated mycobacteria, such as BCG or tyrosinus bacteria, to Freund's adjuvant, otherwise, it is incomplete Freund's adjuvant. When using Freund's adjuvant, the water-in-oil process (that is, emulsification) must be completed, otherwise it will not function as an adjuvant. Alum adjuvant is not good. Freund's adjuvant is commonly used, but when the laboratory lacks lanolin, or the adjuvant is difficult to emulsify after adding a certain virus, alum adjuvant can also be used (see Appendix for formulation). Adjuvants for humans are usually adsorbed on potassium aluminum sulfate or aluminum hydroxide in the form of antigen precipitates, and inactivated Bordetella pertussis is added to improve the immunity of the antigen.
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