What is the practical application of immunology in modern medicine?

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What are the practical applications of immunology in modern times?

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Practical application of immunology

Artificial immunity and biological products

Immunology as a research method

Diseases related to the immune system

Artificial immunity and biological products

Vaccination of smallpox vaccine is the first precedent for human beings to learn to use immune methods to prevent diseases, which has a history of more than 200 years. This method is very effective, so smallpox, a once harmful viral infection, has almost disappeared in human society. In modern times, a variety of products for artificial immunity can be produced on a large scale, which are collectively called biological products. Biological products are widely used in the prevention, treatment and diagnosis of infectious diseases.

1) artificial active immune biological products

Biological products themselves are antigenic components. Injection of antigen components can make human body produce corresponding antibodies, so it has the ability to resist corresponding viruses or bacteria. There are two kinds of traditional antigen components: (1) BCG vaccine, a live vaccine to prevent tuberculosis, is a live mycobacterium tuberculosis, but it becomes attenuated or nontoxic after treatment, so the dosage should still be controlled during injection. The commonly used polio vaccine and paralysis vaccine are live vaccines. (2) Dead vaccines-pertussis vaccine, typhoid vaccine, etc. It is safe to be injected with dead bacteria. However, multiple vaccinations are required. Later, new varieties such as toxoid and subunit vaccine were developed. In recent years, genetically engineered vaccines have been gradually applied. On the basis of finding the surface antigen protein of pathogenic microorganisms, one or even several genes of the surface antigen protein were cloned by genetic engineering and expressed in large quantities, and the effects of good safety, high titer and multi-resistance were obtained. For example, the influenza virus hemagglutinin gene and herpes simplex virus gene are combined into the vaccinia genome to produce a multivalent vaccine that can be inoculated by acupuncture.

2) Artificial passive immune biological products

Biological products themselves are components of antibodies (or antiserum containing antibodies). Injecting antibody components makes people passively gain resistance to corresponding pathogenic bacteria or toxin proteins. Among them, all kinds of antiserum are more specific. Such as anti-rabies virus serum, anti-Japanese encephalitis virus serum and anti-tetanus toxin antiserum. However, immunoglobulin products are not specific. For example, injection of placental globulin or plasma R- globulin is actually an antibody component, which increases the non-specificity of human body.

Immunology as a research method

Because of the specificity of antibody-antigen binding, people often prepare antibodies against protein for the detection and separation of protein. Sometimes antibodies against a small peptide chain or sugar chain can be prepared, but adjuvants should be added to enhance the immune effect; Or connect a small peptide chain to a large protein molecule to enhance immunogenicity. This small peptide chain is called hapten. Enzyme-linked immunosorbent assay (ELISA) is a commonly used immunoassay method for the determination of trace protein, which has strong specificity and high sensitivity, and can detect protein as small as 10-9 grams.

monoclonal antibody technique

Faced with the increasing demand for antibodies-large quantity and high quality, the traditional method has exposed its inherent shortcomings: on the one hand, this set of operating procedures is too complicated, and it is difficult to mass produce animals through immunization and blood drawing; On the other hand, the antiserum obtained is often polyclonal, that is, there are not only antibodies against target antigens, but also antibodies against non-target antigens. As far as the antibody against the target antigen is concerned, a large protein often has several antigenic determinants, and the obtained antibody is also a mixture of each antigenic determinant.

The emergence of monoclonal antibody technology has solved the above two problems.

Mice immunized with target antigen (such as antigen A) have a large number of B cells in their spleen, which can secrete antibodies against antigen A, but these mature B cells can no longer divide and reproduce. Lymphoma cells have the ability to multiply indefinitely, but they cannot produce antibodies against an antigen. The hybridoma cells produced by the fusion of two kinds of cells have both advantages, can secrete specific antibodies against antigen A, and can proliferate indefinitely.

Diseases related to the immune system

1) Allergy and transplant rejection

Strictly speaking, both of these conditions are normal responses of the immune system. Some people are allergic to pollen, and asthma occurs every pollen season. Some people are allergic to a certain kind of protein, and they have a "rash" after eating it. Some people are allergic to bee venom, which can cause shock after being stung by bees. These conditions all originated from the activation of B cells by exogenous substances (pollen, protein, etc.). ), and the antibody produced by B cells acts on mast cells, which makes mast cells secrete excessive neurotransmitter-histamine. Many allergic reactions are caused by excessive histamine in a certain part of the body in a short time. So many desensitizing drugs are related to the effect of antihistamines.

Skin, organ and limb transplantation usually causes immune rejection, which should be said to be the rejection and attack response of normal body to foreign objects. In order to transplant successfully, it is necessary to use immunosuppressive drugs to suppress the normal immune response and give the graft a chance to survive.

2) autoimmune diseases

According to the theory of clonal selection, in the development process of human immunocompetent cells, those lymphocyte clones targeting protein were eliminated. Therefore, mature B cells will not secrete antibodies against their protein, and mature T cells will not attack their normal cells. Because of a special situation, immunocompetent cells mistakenly attack their own tissues and organs, which is autoimmune disease. Common autoimmune diseases include rheumatoid arthritis, lupus erythematosus and rheumatic fever. Some diabetics also destroy islet cells due to the accidental attack of their own immune system, so that insulin can not be secreted normally. At present, the understanding of autoimmune diseases is still superficial, the pathogenesis is not very clear, and the treatment is not very effective.

3) Immunodeficiency.

The low or lack of immune function may come from several reasons, and as a result, the patient's resistance is weakened and it is easy to be infected. Some children are born with severe comprehensive immune deficiency syndrome (SCID). Due to the lack of a gene encoding adenine deaminase (ADA), both B cells and T cells can't develop normally, and such children have to be placed in a sterile and isolated environment at birth (see lecture 6). 1990, gene therapy for children with SCID. Bone marrow cells were extracted from children's bone marrow, and ADA gene was delivered into bone marrow cells by genetic engineering with retrovirus as the carrier. ADA gene is integrated into the chromosome of the cell, and bone marrow cells develop into normal lymphocytes. Then inject it back into the child's bone marrow. The treatment has achieved good results. 4-year-old children with normal lymphocytes and normal resistance can go out of the isolation room and go to kindergarten with other children (see related pictures in lecture 6). Immunodeficiency may also be caused by tumors. During the development of cancer cells, they often secrete some components that inhibit immunity, so cancer patients usually show low immune function. Surgical resection can not only avoid spread, but also eliminate the root cause of immunosuppression. Usually after surgical resection, some drugs to activate and improve immune function will be added. Postoperative chemotherapy has a strong destructive effect on bone marrow cells. Therefore, chemotherapy can also cause low immune function, and it is more necessary to use drugs to improve immune function at the same time. It is worth mentioning that emotions will affect immune function. An optimistic and positive mental state is conducive to the normal play of immune function, while depression and sadness will lead to low immune function. This just reflects the regulation of the brain center on the whole body function.

4) AIDS

AIDS is short for Acquired Immunodeficiency Syndrome (AIDS). It is generally believed that the cause of AIDS comes from the invasion of T cells by HIV. After HIV invades T cells, it can also combine with the chromosomes of host cells and proliferate continuously. The consequence is that the patient loses immunity. AIDS is a sexually transmitted disease. The research on AIDS and HIV has attracted great attention all over the world.

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