Immunity Flashcards
What is self
Material made by the body’s cells
What is non self
Foreign material
What happens if the body is infected with foreign materials?
If a person becomes infected with foreign material, the immune system is activated and attempts to remove the foreign material before it causes harm to tissues in the body.
What is infection?
Infection is entry into the body of a micro-organism that may cause disease. Infection does not necessarily lead to disease.
The immune system has two kinds of response to the entry of foreign material. Which include:
- nonspecific immunity: natural immunity
- specific immunity: adaptive immunity
What does nonspecific immunity involve?
Nonspecific immunity involves many physical and chemical barriers to infection and is not affected by prior contact with a particular micro-organism. It has no ‘memory’ of a prior infection.
What does specific immunity involve?
This defence is highly specific. Specific immunity involves the production of specialised cells and chemical substances known as antibodies, which act against a particular infec- tion. Specific immunity has a ‘memory’
What is the first line of defence?
This first line of defence against infection takes place at the body surfaces. Which includes: - skin - mucus - natural flora - natural secretions
How does skin assist the first line of defence?
Intact skin acts as a barrier against entry by micro-organisms. Glands in the skin secrete fatty acids and sweat contains salt, both of which prevent bacteria.
How does mucus membranes assist the first line of defence?
Mucus secreted by the cells lining your respiratory tract traps bacteria, which are then swept upward to the back of the throat by the action of cilia, which line much of the respiratory tract. Some of the mucus and bacteria are swallowed. Some are removed when you blow your nose. Some bacteria are also removed from the respiratory tract when you cough or sneeze.
Mucus that lines the digestive tract forms a protective barrier and makes it difficult for micro-organisms to penetrate the cells beneath.
How does natural secretions assist the first line of defence?
Tears and saliva con- tain lysozyme, an enzyme that causes bacteria to lyse or burst. Acid in the stomach kills many bacteria.
How does natural flora assist the first line of defence?
Many different bacteria are normally found on the skin, in the gut and (in females) in the vagina. These bacteria are the natural ora of the body and are generally nonpathogenic in those areas. The presence of these bacteria inhibits the growth of pathogenic bacteria in those places because they compete more successfully for the space and nutrients that are available.
In special circumstances, such as when a person takes antibiotics, the natural ora may be disturbed. Pathogenic organisms are then able to move in. This type of infection is called opportunistic infection.
What makes up the second line of defence?
- phagocytes and killer cells
- complement proteins
- interferon
- cytokines
What are phagocytes?
Phagocytes are white blood cells that engulf and destroy micro-organisms and other foreign materials that enter the body, in much the same way as an amoeba engulfs its food.
Where are phagocytes produced?
Phagocytes are produced by cells in the bone marrow and include neutrophils, the most common of the white blood cells, and monocytes, the largest of the white blood cells.
What occurs after a bacteria is engulfed by a phagocyte?
Immediately a bacterium or other micro-organism is engulfed by a phagocyte, enzymes and other factors are released into the vacuole containing the bacterium and the bacterium is killed. Some material may be used by the cell, and unwanted material from the dead bacterium is released by the phagocyte.
What are natural killer cells?
Some white blood cells that kill virus infected body cells
What do other white blood cells do?
Other white blood cells attach to, and help destroy, larger blood parasites such as worms that are too large to be engulfed (phagocytosed).
What are complement proteins?
group of blood proteins that play various roles in the body’s second line of defence against infection. There are 20 different complement proteins.
Where are complement patients made?
They are made in the liver and circulate in the blood in an inactive state. When infection occurs, antibody–antigen complexes form and these activate complement proteins.
What occurs after one complement protein is activated?
The activation of one kind of complement protein results in a cascade effect where each activated complement protein then activates another, and so on down the chain.
How does complement proteins assist in the second line of defence?
Some complement proteins stick to invading micro-organisms, which then become more readily identi able to phagocytes as foreign. Some stimu- late phagocytes to become more active. Some attract phagocytes to the site of infection. Other complement proteins destroy the membranes of invading micro-organisms.
Complement proteins also play a role in acquired immunity
What are interferons?
group of proteins secreted by some cells, in response to a virus infection, that help uninfected cells resist infection by that virus
Why are interferons important?
Interferons are particularly important if a virus does not have far to travel. This is the case with cold and in uenza viruses that infect cells in the nose or throat. Because infection occurs quickly, the body sometimes does not have the time to develop antibodies against these viruses and relies on interferon for its defence. If a person develops a cold or u, interferon has failed to prevent infection.
What do interferons do and produce?
Interferons are produced very early during a viral infection and are particularly important in our ability to resist some viral infections. They cause dozens of antiviral proteins to be made.
What at cytokines?
Cytokines are protein molecules that act as messengers between cells.
What are cytokines produced by?
produced by virtually all cells of the immune system, but particularly by certain T cells. Hence, cytokines act as the messengers between cells of the immune system in much the same way that hormones act as the messengers within the endocrine system.
What do cytokines communicate with?
Cytokines also communicate with cells in other body systems, including the nervous system. As in other cellular communicating systems, a cell can respond to a message from a cytokine only if it has an appropriate receptor. A cell must also regulate the dur- ation of its response to cytokines in order to maintain its proper functioning.
What is inflammation?
reaction to an infection, typically associated with reddening of the skin flowing to an increased blood supply to that region
What is an inflammation reaction?
Inflammation is a reaction to the infection and occurs when arterioles in the area around the cut dilate, resulting in an increased blood supply to the area.
What controls inflammation?
Inflammation is controlled by a number of plasma enzyme systems and other compounds, including serotonin, produced by mast cells, platelets and basophils. Serotonin increases dilation of arterioles and permeability of vascular tissue. The blood carries phagocytes to the area. Phagocytes also move from nearby tissues towards the cut.
Phagocytes at work:
Capillary walls in the area become more permeable to phagocytes, which move out of the capillaries into the surrounding area. Phagocytes that arrive early at the scene of the injury release chemicals such as histamine that attract more and more phagocytes to the infection.As the invading Clostridium tetani bacteria are killed and engulfed by the phagocytes, material that has leaked from the capillaries forms a clot around the infection and prevents its spread. You will probably also have pus in the inflamed area. Pus contains white blood cells that are dead as a result of the many bacteria they have engulfed. It also contains living white blood cells as well as other cell debris. Eventually the pus and other dead or damaged cells are reabsorbed by other cells of the body or released from the skin, and tissue repair occurs. Your skin heals and all outward signs of the infection disappear.
All of the features discussed in this section are nonspeci c in their action.
Exactly the same responses would have operated whatever micro-organism or foreign material you encountered and whether or not you had been previously infected by the organism.
What occurs during the specific immunity?
Once a micro-organism enters your body, the presence of this foreign material initiates a response known as the third line of defence. This line of defence involves a specific response by the immune system to that particular infection and results in adaptive or acquired immunity. The specific immunity acquired is generally long lasting, often for life.
What is the third line of defence?
involves special white blood cells known as lymphocytes. They recognise invading cells or particles, react to that invasion and ‘remember’ the particular type of invader. If the same infection occurs again, the response to it occurs more rapidly.
What are the Two main groups of lymphocytes are involved in specific immunity?
All lym- phocytes are produced in the bone marrow. Some mature in the bone marrow into B lymphocytes or B cells. Other lymphocytes leave the bone marrow before they are fully developed and travel to the thymus gland where they differentiate into mature T lymphocytes or T cells
What are the cells of the third line of defence?
There are different kinds of B and T cells
How do b cells and t cells identify
foreign material?
Proteins on cell membranes are determined by genes. These genes are called the major histocompatibility complex (MHC) and the proteins produced by these genes are called markers. All cells have MHC markers on their surfaces.
