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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Fundamentals of immunology. History and essence of scientific discovery
Directory / The most important scientific discoveries Among the infectious diseases to which mankind has paid tribute with their lives for centuries, smallpox occupied one of the first places. In Europe in the 440th century, about XNUMX thousand people died from it every year. Even more remained mutilated for life, and sometimes blind. The death rate from smallpox was especially high among small children and the poor. Today we are familiar with smallpox only from books. And this is thanks to smallpox vaccination. In our country, smallpox has been eliminated since 1937, and around the world it disappeared by 1980. And humanity should thank Edward Jenner, an English doctor, for this. Interestingly, Jenner discovered a way to prevent smallpox when no one knew the causative agent of this disease. Observation, diligence, purposefulness helped him. Jenner was a simple country doctor when he noticed that people who contracted "cowpox" did not develop natural human smallpox. The fact is that in some animals: cows, pigs, donkeys and others - there is a disease very similar to human smallpox. In animals, purulent vesicles appear on the udder and skin. Milkmaids told Jenner that they all, as a rule, fall ill with cowpox and only then are not afraid of smallpox. Only sometimes during the epidemic, some of them felt a little unwell. For many years, Jenner studied the issue before he decided to conduct an experiment on a person. And so, on May 14, 1796, he inoculated an eight-year-old boy, John Phipps, with pus from the hand of a woman who had contracted cowpox. A few days later, after a slight indisposition, the boy was completely healthy. But has he become immune to smallpox? A different experience was needed, a very risky one, when not only the health but also the life of the child would be at stake. Soon an epidemic of smallpox breaks out in this area. And Jenner, taking pus from the patient's vial, infects John Phipps with it. The child did not get sick! The method of smallpox vaccination was not immediately recognized in the world. The churchmen were very angry, considering this contrary to God. Many doctors were skeptical about him. There were even rumors that vaccinated people grow horns and a tail. And yet, smallpox vaccination won. Dying in 1823 at the age of 74, Jenner knew that his method of fighting smallpox was a boon to mankind. Commemorative medals were knocked out in his honor, monuments were erected in the cities. But the scientific meaning of smallpox vaccination was still unknown at that time. It remains to wait another 58 years until it does Louis Pasteur. Pasteur, unlike Jenner, created a scientific method applicable to all infectious diseases and based on precise experiments. By the seventies of the nineteenth century, Pasteur's scientific merits were universally recognized. In 1872, the Austrian government awards him a prize for his work on silkworm diseases. In 1873 he was elected to the French Medical Academy and in the same year received a gold medal from the Royal Society of London. The French government assigns him a national subsidy for life. In 1879-1880, the scientist studied chicken cholera. “He isolated the culture of the causative agent of this disease and, regularly reseeding it on nutrient media, he was always convinced that the introduction of these bacteria to chickens inevitably caused their death at the latest in two days,” writes A.A. Imshenetsky in his book. It turned out that he did not re-sow the culture and it stood in a thermostat under aerobic conditions for a long time. these bacteria, and those that had previously been injected with a culture that was in a thermostat and did not cause their death. The results of these experiments turned out to be somewhat unexpected. All chickens that were previously injected with bacteria remained alive, those that were not previously injected with culture, soon died. The repetition of experiments gave the same results. These, it would seem, very modest experiments in their results allowed Pastor to come ty to the conclusion that: 1) long-term storage of the culture of the causative agent of chicken cholera in a thermostat with access to air leads to a weakening of its virulence; 2) the preliminary introduction of a weakened culture to chickens makes them immune to this disease. Thus was born the idea of protective vaccinations, which was then used by Pasteur in his subsequent work with pathogenic bacteria. It is difficult to overestimate the significance of the conclusion that he drew from these observations. A principle was found, the application of which became real in relation to a wide variety of infections. Broad prospects have opened up for experimental changes in virulence in pathogenic cultures in order to obtain the material necessary for inoculation. Some of Pasteur's contemporaries in every possible way emphasized the "accidental" nature of the discovery, but sometimes they tend to overestimate the role of chance in scientific discoveries, not realizing that the most significant thing lies not in the observation itself, but in the ingenious ability of the experimenter to generalize and foresee. The principle of weakening the virulence of pathogenic bacteria, established by Pasteur in his studies with chicken cholera, allowed him to conduct similar experiments with anthrax. This microbe formed spores, and it is obvious that it did not make sense to introduce spores of a pathogenic microbe into a living organism. Having established that at 42-43 degrees Celsius the anthrax causative agent grows, but does not form a spore, Pasteur subsequently dealt with it in exactly the same way as with the causative agent of chicken cholera. He received a microbe that lost its virulence to some extent, but retained its immunogenicity. Testing of such cultures revealed that their administration to animals leads to the fact that the latter no longer die when they are injected with a virulent culture. After Pasteur's report on this discovery, the last test remained at the Academy of Sciences - a mass experiment on farm animals in the presence of a commission and veterinary and medical doctors who were interested in the result of vaccination, as well as the general public. Such a test was carried out on May 31, 1881, at a farm in Puyil Fort. The results of the public trials were brilliant. All sheep, which after a certain period of time after vaccination was injected with a virulent culture of anthrax, remained alive, all animals that were not vaccinated died. The beneficial effect of vaccinations has also been proven in cows. Soon this method became widespread throughout the world, and anthrax disease in farm animals became rare. Work on chicken cholera and anthrax allowed Pasteur in 1881 to speak in London at the International Congress of Physicians with a report on vaccinations for these diseases. The report was a great success, and Pasteur's name became widely known in the medical world. There is no doubt that Pasteur's research, which led him to the development of the method of preventive vaccinations, not only laid the foundations for a new science - immunology, but made possible the development of one of the most important sections of preventive medicine. However, the transfer of these data to other infectious diseases was hampered by the fact that their pathogens had not yet been discovered. Therefore, Pasteur continued to look for microbes that cause various diseases. Pasteur's most outstanding work in the field of medical microbiology must undoubtedly be considered his study of rabies, which ended with the proposal of anti-rabies vaccinations. “Checking the infectivity of the brain of animals with rabies,” notes Imshenetsky, “Pasteur found that infection with the brain gives much more positive results than infection with saliva. Further, he was convinced that the introduction of the substance of the brain of a sick animal directly into the brain of a rabbit leads to a significant reduction in the incubation period disease, and successive passages of the virus on rabbits make it possible to obtain a virus that causes disease in just seven days.The brain of a sick rabbit, suspended in a glass vessel over caustic soda, gradually dries up and at the same time the virus contained in it weakens.Repeated introduction of such a brain in the form mashed with saline solution to a healthy animal makes it immune to rabies.The dogs that were given these vaccinations were placed in cages with rabid dogs.The latter bit the vaccinated animals, but despite this, none of them fell ill with rabies.Rabies - a terrible, but relatively rare disease in humans, so it was quite obvious that it was not advisable to vaccinate healthy people, since there was little chance of being bitten by a rabid animal. At this point in his research, Pasteur had the brilliant idea of taking advantage of the fact that rabies usually has a very long incubation period. He suggested that by injecting a stronger and stronger virus into a bitten animal, immunity could be obtained before the virus that was bitten could spread through the body and cause disease. This assumption was fully confirmed. Dogs bitten by a rabid dog were injected with mashed rabbit brain containing the virus. First, a brain that had been drying for a long time, i.e., containing a weakened virus, was injected, and then a less dried brain with a more active virus. These experiments found that the introduction of a weakened rabies virus prevents the disease of a dog bitten by a rabid animal." The task was solved - it was possible to find a method that allowed saving people from a painful death. The next step - to start vaccinating a person - was complex and difficult for Pasteur. The impetus was the arrival in Paris in July 1885 of a nine-year-old boy, Joseph Meister, bitten by a mad dog. He was the first to whom, after great doubt and hesitation, Pasteur was vaccinated against rabies. As a result, the boy did not get sick. October 27, 1885 Pasteur made a presentation at the Academy of Sciences on the results of his research on rabies. The report made a very big impression and caused a standing ovation in honor of the great scientist. The importance of Pasteur's vaccination method is evidenced by the fact that after his work, scientists from all countries developed protective vaccinations against almost all known infectious diseases, both bacterial and viral etiology. They sharply reduced the incidence of these diseases in the population and made it possible to almost completely eliminate individual infections. Exceptionally great successes in this area have also been achieved in veterinary medicine, since the protection of farm animals from a number of epidemic diseases depends on timely vaccinations. Pasteur never believed that immunity could only be achieved by the administration of a vaccine containing bacterial cells. All subsequent successes in immunology, in particular the development of the method of serotherapy, in which Pasteur's students took an active part, are only a logical development of his ideas, which formed the basis of the doctrine of immunity. Author: Samin D.K.
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