Nonspecific immunity refers to the natural resistance to pathogens and has no special targeting. It is gradually formed in the process of biological evolution, so it is not only unique to individuals, but also inherited by species. It is closely related to the tissue structure and physiological function of the body. In the process of anti-infection, it has a quick effect and a wide range, and is the first line of defense against infection. Nonspecific immunity mainly includes the following five aspects: the barrier function of skin, mucosa and barrier structure, and the filtering function of lymphatic tissues (lymph nodes, spleen, etc.). ), the bactericidal effect of serum, body fluids and tissue secretions, the phagocytosis of mononuclear-phagocytic system and the pathological defense of inflammatory reaction.
2. Specific immunity
Specific immunity is also called "acquired immunity". It is an immune function produced by human contact with antigen substances in life and formed after birth. It is characterized by specificity, for example, patients who have suffered from typhoid fever only get immunity to typhoid bacilli. But it has no resistance to other pathogenic bacteria. Specific immunity is divided into natural immunity and artificial immunity. Natural immunity is to gain immunity to a disease by natural means, such as because the body is infected. This immunity can be maintained for a long time, even for life. For another example, the antibodies obtained by the fetus through the maternal placenta and the antibodies obtained by the newborn baby through colostrum can make it difficult for the baby to get some infectious diseases, such as measles and diphtheria, in a short period of time (usually six months) after birth, which is also natural immunity. Artificial immunity refers to the immunity acquired by the human body after vaccination. The immune period can last for several months to several years, which plays a great role in the prevention of infectious diseases; Or inject antibodies into the human body to gain the ability to fight infectious diseases. These are called "artificial immunity". The latter has a short validity period, generally 2 ~ 3 weeks. It is often used to treat or temporarily prevent some infectious diseases.
3. phagocytosis.
The process of swallowing external solid substances into cells. Phagocyte particles are wrapped by a membrane from plasma membrane, which is called phagocyte. The latter is close to lysosomes, and their membranes fuse with each other to form digestive vesicles; The indigestible residue is excreted outside the cell. Some protozoa (such as amoeba) absorb nutrients from it. The cells in the reticuloendothelial system of metazoa can devour bacteria, dust and various colloids, and have defensive functions, which are called phagocytes.
4. Antigen
Any substance that can stimulate human body to produce antibodies and cellular immunity, and can bind antibodies is called antigen. Most protein and bacterial polysaccharides can stimulate human immune response, including the production of antibodies or immune cells.
5. Antibodies
A globulin formed by human body under the stimulation of antigen substance, which can specifically bind to antigen. It exists in blood, lymph and tissue fluid. Antibodies used to be called gamma globulin, but now they are all called immunoglobulin.
6. Vaccines
Active immune preparation is made of pathogenic microorganisms and their metabolites by artificial attenuation or inactivation. In the past, immune preparations made of viruses or rickettsia were called vaccines, vaccines made of bacterial cells, and toxoids made of bacterial exotoxins by formaldehyde detoxification. In recent years, with the improvement of preparation methods of immune preparations, active immune preparations used for vaccination are collectively called vaccines. There are many ways to classify vaccines, and vaccines are often divided into attenuated live vaccines and inactivated vaccines (dead vaccines) according to their nature. Live vaccine is made of attenuated or nontoxic pathogenic microorganisms (bacteria, viruses, etc.). ). After inoculation, it can grow and reproduce in human body, but it doesn't get sick. It has long action time in vivo, good immune effect and few inoculation times, but it is not easy to preserve. Such as measles vaccine and BCG vaccine. Inactivated vaccine is made by inactivating pathogenic microorganisms by physical or chemical methods. Inoculation can stimulate the body to produce specific immunity. Because this kind of vaccine can't grow and reproduce in human body, it is relatively safe and stable, but it has short stimulation time and low immunity. It takes many injections to produce relatively stable immunity. Such as DTP mixed vaccine, Japanese encephalitis vaccine and so on.
7. Development of vaccines
Since the beginning of mankind, diseases have always been the enemy of mankind, especially infectious diseases. In the Middle Ages, the epidemic of deadly infectious diseases such as smallpox, plague and cholera caused great disasters to Europe and even the world. Among these infectious diseases, some are caused by bacteria and some are caused by viruses. The discovery of various antibiotics in the 20th century made bacterial infection no longer a problem for doctors. However, virus infection, such as AIDS and SARS virus, still puzzles human beings, which will be another challenge to science and technology and human beings.
Bacteria and viruses are the culprit.
Bacteria are single-celled organisms that can be killed by antibiotics and various chemicals. Viruses are acellular organisms, and only vaccines can destroy them. Antibiotics have no effect on them. The pathogen of atypical pneumonia prevalent in China and even the whole world is a coronavirus. Viruses are much smaller than bacteria. Bacteria usually take micron (mm,11000 mm) as the unit of measurement, while the unit of measuring virus size is nanometer (nm, that is,11000 micron). Because the virus has the function of self-replication, it is much more difficult to develop effective non-toxic antiviral drugs than antibacterial drugs.
Antibiotics only act on bacteria and have no effect on various virus infections. Compared with antibiotics, the composition of vaccine is more complicated, and it is a mixture of various protein or sugars, which is mainly used to prevent various infectious diseases. Use before onset, but generally not when onset. Each microbial vaccine can only prevent the corresponding diseases and has strong specificity. After the vaccine is immunized, the body can produce specific antibodies. When this pathogen invades the human body, the antibodies in the body are immediately recognized, combined with the pathogen, and a series of mechanisms are started, and finally the pathogen is eliminated.
The struggle between vaccines and viruses has a long history.
Before people observed the existence of microorganisms with various instruments, people had recognized the existence of infectious diseases, and the prevention of infectious diseases through immunization left a brilliant chapter in the history of human existence.
Smallpox is the first fatal viral infectious disease recorded in human writing. The symptoms are fever and vomiting, rash, papules, herpes and pustules, and finally atrophy. The patient is either scarred, blind or dies before the rash bleeds. Immune prevention of smallpox is a successful example of human control and eradication of infectious diseases. It is speculated that smallpox may have existed on the earth120,000 years ago. Smallpox was introduced to China in the 2nd and 3rd centuries, to America in the16th century and to Australia in the18th century, and all countries in the world were spared. During the smallpox epidemic, 1 person died in every four infected people. The traditional folk treatment in China is to crush the shriveled scab of smallpox patients and blow it into the nostrils of smallpox patients. At present, there is no record of how China people got this method to treat smallpox, which may be caused by the method of fighting poison with poison that China people are proficient in, but this method can really prevent the malignant development of smallpox patients' symptoms.