Understanding Your Body’s Defenses: Immunity Explained
1. Body’s Defense Mechanisms
1.1 External Barriers
1.1.1 Physical Barriers
Skin: Infectious organisms can only penetrate the body when the skin is injured. Therefore, it is important to clean and disinfect any wound with soap and iodine solution.
1.1.2 Chemical Barriers
There are different parts of our body where there is no skin, such as the mouth, nostrils, eyes, anus, urethra, and vagina. The mucous lining of these parts secretes substances that kill microorganisms, such as lysozyme.
Lysozyme is an antibacterial substance found in saliva and tears. In the mouth, vagina, and intestines, there are bacteria that defend against other infections.
Sweat: Hinders the proliferation of microorganisms and is effective in cooling the skin.
Fat: Secretion of the sebaceous glands of the skin that hinders their proliferation.
1.1.3 Biological Barriers
These are non-pathogenic microorganisms, meaning they do not cause disease and inhibit the invasion of pathogens into the skin or mucous membranes.
1.2 Internal Barriers
If infectious microorganisms are able to pass through the skin, the body involves several types of white blood cells.
1.2.1 Nonspecific Immune Response
Monocytes: These are a class of white blood cells that leave blood vessels and can move between cells of tissues. They are responsible for phagocytosis of pathogens and are also called phagocytes or macrophages.
1.2.2 Specific Immune Response
Lymphocytes: These are another type of white blood cells capable of recognizing any foreign substance or molecule in our body, called antigens.
In the presence of a specific antigen, such as microbes (bacteria and viruses), lymphocytes secrete antibodies. Each antibody is specific to its antigen.
When the body comes into contact with an antigen and produces the corresponding antibodies, lymphocytes are able to become cells that store the information to produce faster and a greater amount of specific antibody. This is the memory immune response.
2. The Immune System
The immune system is formed by the bodies which produce white blood cells.
The red bone marrow: The red bone marrow is where most white blood cells are produced. Among these, lymphocytes, which are cells that produce antibodies, have already matured in the thymus, in the same red bone marrow, and liver.
In Peyer’s patches of the small intestine, the spleen, and lymph nodes, different types of lymphocytes can be produced.
2.1 Immunity
Immunity is the ability to be invulnerable to a particular infectious disease. This is achieved by means of antibodies, and these antibodies may come from different places.
2.1.1 Active Immunity
It is the ability to produce specific antibodies after overcoming an infectious disease; this is called immunological memory.
Natural Active Immunity: When a person overcomes a certain infectious disease caused by a microorganism, they create natural antibodies and thus become immune forever.
Artificial Active Immunity: Obtained through vaccination, and the effects can persist for a long time.
2.1.2 Passive Immunity
The body receives antibodies produced previously (the body does not produce them).
Natural Passive Immunity: The antibodies come from the mother through the placenta or colostrum from the mammary glands. This effect lasts during the first three months of the baby’s life.
Artificial Passive Immunity: It provides a serum against a particular disease, for example, a tetanus injection (antibodies against tetanus). This effect is temporary, while the antibodies are effective in the blood.
3. Vaccination
The vaccine is prepared with an antigen that, when injected into the body of a person, causes their immune system to produce antibodies against this antigen. This raises the person’s immunity (active and artificial).
Vaccines consist of an antigen containing dead or weakened viruses or bacteria, which cannot cause any damage or multiply.
Vaccines are not a method for treating infectious diseases, but a method of prevention.
4. Treatment of Infectious Diseases
Each type of infectious disease requires a different treatment.
4.1 Infections produced by fungi are treated with fungicides.
4.2 Infections produced by protozoa are treated with chemicals.
4.3 Infections produced by viruses require waiting several days for your immune system to produce antibodies to fight the infection. In some cases, serotherapy is needed. In others, specific chemicals are designed, such as for the AIDS virus.
4.4 Infections produced by bacteria are treated with antibiotics.