systems of the body that protect it from diseases, infections and harmful influences. This complex system recognizes antigens (bacteria, viruses, fungi, and abnormal cells) and neutralizes or destroys them before they cause harm to the body. Immunity can be divided into main types depending on the mechanisms and characteristics on which it is based:
1) Innate immunity is the body’s first line of defense, innate and characterized by a quick and effective response to any antigen without the need for prior exposure. This immunity includes physiological barriers (skin and mucous membranes), chemical barriers (gastric juice and protective enzymes of saliva and tears), and protective cells (phagocytes and natural killer cells (NK cells)). Innate immunity provides a general, non-specific response, but it is necessary to quickly prevent infection, and also stimulates acquired immunity later on.
2) Acquired immunity – this immunity appears after the effect of antigens on the body. It is characterized by the body’s ability to recognize a specific antigen and respond to it with high accuracy. It also has an immunological memory, which allows it to quickly recognize the same antigen in the future. It is divided into:
– Humoral immunity – based on the production of antibodies by B-lymphocytes that bind to antigens, neutralize them or recognize them for destruction.
– Cellular immunity – based on T lymphocytes that directly target virus-infected or cancerous cells or regulate the response of B lymphocytes and antibodies.
3) Natural and Acquired Immunity:
– Natural immunity – includes the immunity that a person is born with, including some inherited antibodies or innate immunity against certain diseases.
– Acquired or artificially acquired immunity – achieved through the natural effects of disease or vaccination, when the immune system is stimulated to form an immunological memory against a specific antigen, providing effective protection.
4) Active and passive immunity:
– Active immunity – occurs as a result of stimulating the body to produce antibodies and immune cells after direct exposure to an antigen or after vaccination.
– Passive immunity – in which antibodies are transferred in a ready-made form from another source, for example, the transfer of antibodies from the mother to the fetus through the placenta or through breast milk, or the use of ready-made antibody preparations for the treatment of diseases (serums).
5) Local and Systemic Immunity:
– Local immunity – protects specific areas of the body, such as the mucous membranes of the respiratory, digestive, and reproductive systems.
– Systemic immunity – The immune response affects the entire body, including the blood, lymphatic organs, and defense cells distributed throughout the body.