Historically immunity meant protection from disease and more specifically infectious disease. The cells and molecules responsible for immunity constitute the immune system and their collective and coordinated response to the introduction of foreign substances is called the immune response.
Antigens are a wide number of things. They are usually proteins on the surface of cells, fungi, bacteria or viruses, and the body recognizes harmful antigens and protects itself from them. Antigens also come in the form of nonliving substances, like chemicals, drugs, foreign particles and toxins.
The immune system is able to learn which antigens are not harmful, such as ones in our own body’s cells. The body doesn’t react to these non-harmful antigens, usually.
We are born with a protection system in our bodies called innate immunity, and this protects us against antigens. This innate immunity involves certain barriers of defense, such as:
- Cough reflex
- Enzymes in tears and skin oils
- Mucus, which traps bacteria and small particles
- Stomach acid
This innate immunity also comes in a protein chemical form, called innate humoral immunity. Examples of this kind of immunity include the body’s complement system and substances called interferon and interleukin-1 (this causes fever).
Antigens that make it past these barriers are attacked and destroyed by other parts of the immune system.
In contrast to innate immunity, acquired immunity is developed as you’re exposed to various antigens, and your body builds a defense to those antigens.
A pregnant mother passes antibodies to her infant through the placenta, which is an example of passive immunity. These antibodies disappear between 6 and 12 months of age.
Passive immunization, involves the injection of antiserum which contains antibodies that are formed by another person or animal. This immunization provides immediate protection against a certain antigen, but the protection doesn’t last. Examples of passive immunization include Gamma globulin (given for hepatitis exposure) and tetanus antitoxin.
Certain types of white blood cells are an important part of the immune system. Certain chemicals, proteins in the blood, like antibodies are also part of the defense. Some of these things directly attack foreign substances in the body, while others work to aid immune system cells.
B cells: Produce antibodies, which attach to a specific antigen and make it easier for the immune cells to get rid of it.
T cells: Attack antigens directly and help control the immune response. T cells also release chemicals known as interleukins which serve to direct the entire immune response.
Developing lymphocytes normally learn to differentiate between normal body tissues and substances not normally found in the body. B cells and T cells form, and a few of them provide memory for the immune system, making the body more prepared for second attacks from the same antigen. Chickenpox immunizaton is a good example.
Bacteria, trauma, heat, toxins and many other things can injure the tissue in a person’s body, causing inflammation. The damaged tissue releases chemicals including histamine, bradykinin, and serotonin, which cause blood vessels to leak fluid into the tissues, resulting in inflammation. This swelling keeps the foreign substance from further contact with body tissues.
These same chemicals attract white blood cells called phagocytes that “eat” microorganisms and dead or damaged cells, a process called phagocytosis. Pus is formed by a collection of dead tissue, dead bacteria and dead and live phagocytes.
Immune System Disorders and Allergies
The immune response is a complicated one, as are many procedures of body. The immune response in some people misbehaves, meaning that when a foreign antigen arrives, the body either reacts excessively or not enough, or inappropriately. Allergies are when a person experiences an immune response to a substance that most bodies perceive as harmless.
There are reliable ways around these inappropriate immune system responses. Vaccination, also called immunization, is a way to trigger the immune response. Small doses of an antigen, dead or weakened live viruses for example, are given to activate the B and T cells into remembering the antigen. This memory serves to block the antigen in the future, giving the immune system the tools it needs.
Complications Due to an Altered Immune Response
Why is it bad to have an immune response that doesn’t function properly? This immune response is important for protecting you against diseases and disorders, which means an inefficient system can allow diseases to develop.
Complications related to altered immune responses include:
- Allergy or hypersensitivity
- Immunodeficiency disorders
- Autoimmune disorders
- Blood transfusion reaction
- Disease development
- Graft versus host disease
- Serum sickness
- Transplant rejection