Immune System

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* Enzymes‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎‏‏‎ ‎ ‎‏‏‎ ‎‏ ‎‏‏‎ ‏‏‎ ‎‏‏
* Lymphoid organs

### Function

Get rid of undesirable or dangerous organisms, such viruses and bacteria, Eliminate malignant or contaminated cells, Offer protection against certain illnesses

### Downsides

Allergies, blood cancer, autoimmune disorders, viral infections that spread, and inflammation

### Found in

Nearly in every living thing, Vertebrates

## Kurzgesagt info

### First appearance

The Immune System Explained I – Bacteria Infection

### Latest appearance

How The Immune System ACTUALLY Works – IMMUNE

## General Information

The immune system is a sophisticated network of tissues, cells, and proteins that fights off pathogens and other objects that might endanger the body. Leukocytes, antibodies, and the complement system make up these cells and proteins. They are capable of identifying the majority of pathogens and sick cells, including cancer, viruses, fungus, bacteria, and parasites.

They are all linked together and comprise hundreds of organs classified into two groups: lymphoid organs. The bone marrow and thyroid are the principal lymphoid organs in the first group; they generate lymphocytes, which are immune cells. The tonsils, spleen, lymph nodes, and other tissues that the immune cells use for training and function belong to the second category of lymphoid organs.

The immune system is divided into two subsystems. The first is the innate immune system, which does not offer long-lasting protection but instead instantly eliminates infections. The other is the acquired immune system, also known as the adaptive immune system, which mounts coordinated defenses against foreign chemicals and proteins. The foundation for vaccine development is the adaptive immune system.

Nevertheless, the immune system is not perfect. Immune system dysfunction can result in cancer and autoimmune illnesses like lupus. A weakened and inactive immune system leaves a person more susceptible to various illnesses, which is known as immunodeficiency. Allergies can arise when the immune system misinterprets harmless substances like pollen and nuts.

### Parts

#### Innate

Because of its simplicity, the innate immune system defends against viruses in basic unicellular organisms like bacteria. They have been present in contemporary living things like plants and insects since their very early emergence, maybe dating back to the time of single-celled eukaryotes.

They are made up of barriers like skin or cell walls that keep infections out, making them incredibly basic and non-specific. The complement system, defensin proteins, and macrophages arrive if they are able to enter through a wound or other hole.

##### Human Innate System Response

The first cell to arrive is a macrophage when a pathogen enters the body by a cut, wound, or aperture such as the mouth, nose, or eyes. Using a process known as phagocytosis, macrophages grasp the bacteria with their extended arms, swallow them whole, and then utilize acid to break them down.

Macrophages communicate with the bloodstream to release fluid and summon neutrophils for assistance. The complement protein, which attaches to the bacteria and makes them easier to trap, is present in the fluid that was expelled. In addition to releasing lethal compounds and creating barriers to keep bugs trapped, neutrophils also poison the bacterium.

#### Immunity

Following the battle, the cells have defeated the bacterium and end their own life to save their host's resources and prevent further harm. Because no memory cells are created, the immunity wears off quickly. You will once again be susceptible to this particular germ after a certain period of time.

The immune cells will kill themselves once the virus has been eradicated in order to limit the amount of damage they may do. Not every cell, though, ends its own life. A small number of memory T and B cells will develop into helper cells and circulate throughout the body, ensuring that the particular bacterium never re-infects the host. In the event that the bacterium assaults once again, the T cells will launch automatic attacks that instantly eradicate the illness. Long-lasting protection against the bacterium is therefore provided. The current generation of vaccinations is based on this.

#### Adaptive Immune System

More sophisticated defense and immunity mechanisms are found in more complex lifeforms, such as vertebrates, which includes humans. Only vertebrates have an adaptive immune system; all other species only have an innate immune system. The adaptive immune system offers lifetime immunity, in contrast to the innate immune system. The goal of vaccine development is to provide long-lasting protection. The many cell types that make up the adaptive immune system are numerous.

##### Human Adaptive Immune System Response for Bacteria

It starts with a pathogen entering the body and multiplying, just like the innate immune system. Once more, neutrophils and macrophages step in. While neutrophils produce poisons and barriers that kill germs, macrophages use their filopodia to ingest the pathogens. Additionally, the complement system performs its function. Macrophages will communicate protein signals to the dendritic cell if any of these three mechanisms are ineffective in stopping the bacterium.

The dendritic cell gathers pathogen samples and presents them to their cell membranes after receiving the signals. The dendritic cell must now decide whether to summon bacteria-killing or anti-virus powers. Let's assume that a bacterial infection is the cause of this case. The dendritic cell choose the latter choice as a result. After that, it takes almost a day to reach the next lymph node where it activates virgin helper T cells, a particular kind of cell.

To identify the cell with the ideal structure, the dendritic cell rubs against the virgin helper T cells. The majority of cells don't, and it takes a while to identify the ideal cell.The virgin T cell will develop into a helper T cell until the dendritic cells locate one. Only 25% of helper T cells survive the rigorous and complex training that they undergo. They progressively withdraw from the lymph node and begin to divide until thousands of them remain. They now divided into two groups. While the other group travels to activate a different type of cell, the first group supports the immune system at the infection site.

The second group proceeds to activate B lymphocytes, which provide an additional line of defense. In short, B cells are our makers of antibodies. Once more, each virgin B cell is unique, therefore the helper T cells need to identify the one with the correct arrangement out of billions. The virgin B cell will begin replicating until it reaches the target population once the T cells locate one. Each B cell has the capacity to manufacture up to 2,000 antibodies every second once they are finished.

The antibodies eventually reach the infection site one week after the infection. They cover the battlefield in billions, squeezing and latching onto the infection to either shock or even kill it. Macrophages are effective in consuming microorganisms that have been captured by antibodies.