Metchnikoff's theory of immunism, or humoral immunity, in contrast to phagocytic immunity, develops earlier and lasts longer. Antibodies (immunoglobulins) circulate freely in the blood and are able to interact with foreign substances and kill them. Some types of immunoglobulins are converted into phagocytes. Immune reactions are very intense. Against their background, inflammatory processes can develop, affecting the respiratory, digestive and excretory systems.