Aggressins

AGGRESSINS, a term introduced by Bail for designating those substances of unknown nature which bacteria secrete in the infected organism and thanks to which they can resist its protective adaptations (phagocytosis, bacteriolysis, etc.) and, continuing to develop successfully within it, cause general infection. Even before Bail's work, it was known that bacteria, passing sequentially through animal organisms, become more virulent than the original strains of cultures (Pasteur's law of passages). It was also proven that some microbes in the animal organism form a well-distinguishable under the microscope mucoid capsule that protects them from the lytic substances of sera and from phagocytosis. Thus, if a guinea pig is injected into the abdominal cavity with an anthrax culture, then in the exudate develop rods covered with mucoid capsules, and none of the rods are phagocytized by the polynuclears present in the exudate; but if at this moment the same rods from an agar culture, where capsules do not develop, are again injected into the abdominal cavity of the guinea pig, then these latter are absorbed by leukocytes. Obviously, the leukocytes have not lost in the presence of bacteria the ability to phagocytize, but it is the rods that have changed, becoming covered with a capsule thanks to which phagocytes do not capture them. The same was proven by Bordet with respect to streptococci. Bail assumed that in exudates some substances are secreted by bacteria that protect them from the cells of the organism; through a series of experiments he showed that such substances are indeed present in exudates. The general setup of the experiments is as follows. The minimum lethal dose of microbes (anthrax, chicken cholera, hemorrhagic septicemias, etc.) is established for an animal of a given species and weight. The animal is infected through the abdominal or pleural cavity. The exudate that has formed at the site of inoculation is collected and sterilized by filtering through a Chamberland candle. To test the action of the filtrate, one series of animals is infected with minimum lethal doses of the microbe being tested; to another series of animals, the same or even smaller doses of microbes are injected, but at the same time the aforementioned filtrate containing the supposed A. is also injected. The animals that received both the infection and the A. die much faster than those that received only the infection, and even those animals that received a dose of microbes less than the lethal dose and would have survived if they had not received aggressins die. 'k* щ&

5^b 1 - 4 - aortic aneurysm. 5a, b, c-aggregate state: 5a - radiogram of a silk fiber; 5b and 5c - radiograms of plant fibers (a bundle of rays is directed perpendicular to the length of the fiber). SEE ALSO Aneurysm of the aorta, Aggregate state. From these experiments, Bail concludes that in exudates some substances secreted by microbes are formed, which he named A., which promote infection. Furthermore, Bail showed that these A., when introduced into animals, after some time (about 10 days) make these animals insensitive to the corresponding microbes. Obviously, A. serve as antigens for the production of antibodies in the organism that protect it from infection; according to the same terminology, these will be anti-aggressins. - A. may not only be present in exudates but also circulate in the blood, as for example, in lobar pneumonia. If one takes from a patient in the height of lobar pneumonia, blood serum which is not poisonous in itself for mice, injects it under the skin to mice and then infects them with a minimal or five times less than the minimal lethal dose of pneumococcus, they will die much faster than those that received the minimal lethal dose without serum; mice that were not treated with serum and received a dose smaller than the lethal one remain alive. Obviously, in the blood during lobar pneumonia at the height of the process, A. for pneumococcus circulate. But if one takes serum from the same patient during the crisis, or after it, then such serum, when injected into mice in certain doses, not only does not promote their illness, but on the contrary, protects them from a tenfold lethal dose of pneumococcus. From the experiment it follows that during recovery, as well as during immunization, anti-aggressins are formed, leading to the disinfection of the patient's organism. The main conclusions of Bail about A. and anti-aggressins were confirmed by Weil and a number of other authors. In the further study of A., Wassermann and Citron showed that these substances are formed not only in animals infected with microbes; they can also be extracted from pure microbe cultures, i.e., they can form outside the animal organism. Filtrates from microbe cultures, when injected into animals, can make susceptible to infection even those animals that, by their natural properties, are completely immune to it, for example, rabbits to cholera (Sanarelli). The essence of the action of aggressins and anti-aggressins - see Antitoxins, Opsonins, Bacteriotropins.