- Provides an immediate nonspecific immune response
- Activates T and B cells in response to an infection
- Responds to a later exposure to the same infectious agent
- Distinguishes self from nonself
The immune system is a system of organs that perform function to protect the host from pathogens a.k.a anything that can cause diseases. The immune system can be separated into two parts, the innate immune system, and the adaptive immune system.
1. The easiest way to tell the difference between the two parts of the immune system is to think of them as lines of defenses. The Innate immune system, the first line of defense, acts like an overall defense. It usually provide immediate nonspecific immune responses. Example of these responses and where they take place are: the skin, which protects our body from most infectious agents, tears and saliva, which flush infections away from our eyes and mouth respectively, and mucous membranes in our mouth and nose that release mucous that traps pathogens. Below is a chart from Wikipedia that gives examples of other places in your body that act as the first line of defense.
| Anatomical barrier | Additional defense mechanisms |
|---|---|
| Skin | Sweat, desquamation, flushing,[4] organic acids[4] |
| Gastrointestinal tract | Peristalsis, gastric acid, bile acids, digestive enzyme, flushing, thiocyanate,[4] defensins,[4] gut flora[4] |
| Respiratory airways and lungs | Mucociliary elevator, surfactant,[4] defensins[4] |
| Nasopharynx | Mucus, saliva, lysozyme[4] |
| Eyes | Tears[4] |
2 and 3. When the first line of defense is not enough, for it often happens, the second line of defense known as the adaptive immune system. This system is composed largely of white blood cells: Neutrophils, Lymphocytes, monocytes, eosinophils, and basophils.
Eosinophils and monocytes swallow foreign particles in the body.
Basophils help to intensify inflammation (swelling).
Lymphocytes attack pathogens and create antibodies that help destroy bacteria.
They are separated into T cells and B cells. B cells mature in the bone marrow whereas T cells mature in the thymus, and are both responsible for developing immunity to specific diseases.
This second line of defense is more specific and also adds diseases into the body's memory for future notice.
B Cells produce antibodies and are able to detect antigens, anything capable of triggering an immune response, man-made, or foreign. When a foreign cell infects the body, the B cell is able to recognize it. It binds to the antigen on the surface of the cell, turns into a plasma cell, and is then able to create antibodies against that cell. This encourages other cells to "eat" that pathogen. The B cells that don't become plasma cells become memory cells and are able to recognize that type of foreign cell easier later.
T Cells directly attack foreign invaders, but cannot detect them like B cells. T cells bind to these foreigners with the help of other cells, but need a signal to activate them. Once they get the signal, they multiply and continue to attack the pathogen. Like B cells, T cells can also become memory cells.
4.
In the body, almost all cells have molecules that determine that cell as "Self."
Immune cells and body cells that are "self" co-exist in self-tolerance.
When immune cells come across cells that do not have these molecule, these cells are marked as foreign, or "noself"
An antigen can be told its foreign by the epitopes on its surface, which distinguishes its shape.
Sometimes the immune system can wrongly determine self or noself, because of autoimmune diseases.
In Cancer, the immune system is very important before, during, and after treatments. Cancer cells can sometimes affect our immune systems, while the cancer treatments can also affect our immune system. Cancer can spread into our bone marrow, which is where many of our blood cells that help fight diseases are created. Chemotherapy and radiotherapy can cause a significant drop in the creation of white blood cells.Because cancer cells, and normal cells have fewer differences than pathogens and normal cells, our body has a harder time detecting cancer cells.
