The Immune System (basic)

Updated: Oct 24, 2019


What does a pathogen cause?

It causes a disease by invading the body.


How is a bacterial infection treated?

A bacterial infection can be treated with antibiotics, considering it is a natural substance, which slows down the growth of the bacteria.

What is the first line of defence, the second and the third?

The first line of defence :

The first line of defence skin, that is a thick barrier protecting the environment on the inside. It is waterproof and has secretions that repel the bacteria. The opening parts on the surface of the body like, eyes and nose are protected by different secretions (tears, mucus, saliva) containing the enzyme Lysozyme. However, when it comes to the nose it already has protection with the “Nose hairs” covering the inside and trapping any bacteria nearby. Lysozymes attack the cell wall of the bacteria. Furthermore, you also have the acidic environment in the stomach that kills the bacteria swallowed.

Second line of defence :

Various functions are included like Phagocytosis, antimicrobial substances, inflammation and fever. Phagocytosis is a form of endocytosis (cell eating). It is a process of ingesting as well as digesting any bacteria or worn out cells from the body = vacuum cleaner. The two most important leukocytes that are phagocytes like macrophages and neutrophiles.

What can phagocytic leucocytes do to be able to pass through capillaries?

Due to the phagocytic leucocytes being able to change shape easily, they can easily squeeze in and out of capillaries. By which process does phagocytic leucocytes kill invaders? What is a phagocyte leucocytes and explain the process of a phagocytosis

Phagocytic leucocytes are a special type of white blood cells that will kill invader through the process of phagocytosis. They engulf the bacterium into a vacuole and release hydrolytic enzymes. The bacteria is then destroyed and all the bacteria which are not absorbed are egested (thrown out). Today we have about 50 antibiotics that work in different ways, why is that efficient in order to kill pathogens? Due to the fact that the prokaryotic and eukaryotic cells have different metabolic pathways, we are in need of different antibiotics. An example would be that some antibiotics can block the protein synthesis mechanism in bacteria while not affecting the process in human cells.

Why do viruses not get affected by antibiotics?

Because viruses are not living and do not have their own metabolic pathway, they cannot be affected by antibiotics since they use the human host's metabolism to make copies of themselves.

What does “ANTIGENS” stand for?

Antigens stands for: Antibody Generating Substances.


Where are antigens found and what can they recognise?

Antigens are found embedded in the plasma membrane or cell walls of bacteria, or in the protein coat of viruses. The Antigens enable to body to recognize the pathogens as “non-selfs”, thus the body switching on its immune response with a rapid production of antibodies.

Are antibodies carbohydrate or protein molecules?

Antibodies are protein molecules.

What is an immune response?

An immune response switches on the rapid production of antibodies with the aim to attack pathogens.

Why is the skin a good barrier?

The skin acts as a thick physical barrier protecting the body from the outside environment. It does this by being a non-favorable environment for Pathogens to live and multiply. The skin poses threats to the pathogens by being dry, having a slightly acidic pH as well as having natural flora which competes for nutrients together with the pathogen.

How are our eyes, nose and mouth protected from pathogens?

The are coated with a thick mucus containing enzymes called lysozymes which break down the cell wall of bacteria as well as the nose is protected with nose hairs which act as filter microbes which traps bacteria.

What shape does an antibody have?

A Y-shape with one part being a constant and the two others being two variables (antigen binding sites).


How do antibodies react?

When an antibody binds to an antigen, it can destroy it in different ways:

  • by causing bacterial cells to clump to simplify the work of phagocytes

  • by causing cell walls to rupture

  • by deactivating toxins

  • by acting as recognition signals for phagocytes giving a clear indication that action is needed.

Explain HIV and AIDS, compare and contrast

HIV: human immunodeficiency virus which infects (only) the helper T-cells (a type of lymphocyte which is important in maintaining communication between the immune system’s cells. When the infection destroys the helper T-cells ( it can take a month to a year) their numbers decrease and so does the body’s ability to fight infections. If we would not have the helper T-cells then their would be nothing that would instruct other Lymphocytes to clone and generate antibodies, thus the body would no longer be able to fight pathogens. HIV is transmitted in blood vaginal secretions, semen, breast milk and sometimes across the placenta.

AIDS is a follow up from HIV infection which is a severe failure of the immune system as the HIV virus selectively infect helper T-cells. The symptoms of AIDS develop in different speeds and occurs as a result of secondary infections caused by bacteria, fungi and viruses that the body is unable to resist due to its compromised immune system (caused by HIV).

How is HIV passed from person to person?

HIV is transmitted in blood vaginal secretions, semen, breast milk and sometimes across the placenta. Thus being passed on by sexual intercurse and giving birth.


What are prions?

Prions are infectious particles that do not contain nucleic acid. They are proteins that converts normal proteins into infectious prion proteins and they can not get destroyed by normal sterilization techniques. Therefore they have been spread on surgical instruments and in contaminated meat. An example of a prion disease is scrapie in sheep.

What happens when a tissue/skin gets damaged? Name the different helpers.

When tissue or skin get damaged the body generates the process of blood clotting. Any blood that escapes from a damaged vessel quickly forms a glott, which plugs the gap and therefore prevent pathogens to enter. Platelets, erythrocytes (red blood cells) and leucocytes (a type of white blood cell) are important in the clotting process.

  • Platelets are small cell fragments which is formed in the bone marrow and circulate the blood stream.

  • Also important are two plasma proteins called prothrombin and fibrinogen, which are present in the blood and are in their inactive form until activated when they are needed. T

What are macrophages, B-cells and T-cells?

Macrophages are bigger and tougher phagocytes and they are white blood cells that have come from the blood into the tissues. These organisms engulfs foreign substances.

B-cells are a type of lymphocyte that have antigens on their surface. Although all B-cells contain antibodies, the antibodies are all different depending on the B-cell. This means that there are specific B-cells for specific pathogens as the antibody need to bind to an antigen to do it’s work. The B-cells then attaches to the pathogen and the pathogen is engulfed. This causes the B-cells to multiply and create memory cells and effector cells.

Helper T-cells activates other cells to fight off the foreign substance.

#Yas #YasAsghari #Firstlineofdefense #secondlineofdefence #Defencesystem

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