The immune system along with the nervous plays an essential role in the process of adaptation of the organism to environmental conditions. These systems interact with each other, although in many cases they behave largely autonomously. Let us briefly consider the organization of the immune system, which protects the body against infectious agents, foreign macromolecules and its own transformed cells (for example, tumor cells). The most important cells of the immune system – the blood leukocytes arise from the hematopoietic stem cells of the bone marrow. Certain types of white blood cells (monocytes, granulocytes, T-and B-lymphocytes) are involved in various immune reactions.
The immune response can be of two main types: non-specific and specific. When a foreign antigen enters the body, the nonspecific immune response develops first. This response includes phagocytosis by blood monocytes and tissue macrophages, as well as inflammatory reactions in which granulocytes take part. In addition, lymphocytes, called natural killers, are able to destroy viral agents and certain types of tumor cells.
If nonspecific immunity is insufficient, then a second level of immune responses develops, which is distinguished by high specificity. Specific immunity is mainly created by B and T lymphocytes. They give the body the ability to respond to a virtually unlimited set of antigens.