Defence Against Diseases Flashcards
What is a pathogen?
An organism that cause disease
What is immunity?
The ability to resist infection
What allows us to resist infection?
The human defence system
What is the general defence system?
It acts as a barrier to all pathogens attempting to gain entry to the human body
What does the general defence system consist of?
First part : skin, mucous membranes and their secretions = prevent entry of all pathogens
Second part : white blood cells and chemicals that destroy any pathogen that penetrate into the body or attempt to gain entry
Examples of the first line of defence
Skin - physical barrier that prevents pathogens from passing through
Clotting - If skin is broken, blood clotting prevents entry of further pathogens [prevents blood loss]
Lysozyme - enzyme found in sweat, tears and saliva which attacks and dissolve the cell wall of many bacteria t
Sebaceous glands - in the skin produce chemicals that kill bacteria [released in sebum oil]
Mucous - pathogens trapped by mucous and prevented from entering the body
Cilia - respiratory system is lined with tiny hairs known as cilia which beat and create a current, which moves mucous back up the respiratory system so that it can be swallowed into the stomach
Acid - hydrochloric acid in the stomach kills pathogens
Beneficial bacteria - in the vagina produce lactic acid which prevents the growth of pathogens
What is the second line of general defence?
Consists of the destruction of pathogens by white blood cells, the production of a series of proteins that kill or prevent pathogens from reproducing and the inflammatory response
What are phagocytise white blood cells
When cells are damaged by invading micro organisms they release a large number of chemicals which attract phagocytes from the bloodstream, the phagocytes engulf and destroy any micro-organisms they meet
What are macrophages?
Large phagocytes. Some move around body in body fluids and act as scavengers for pathogens whereas others remain in fixed places such as steel, lymph nodes and other lymphatic tissues, such as tonsils. They filter out and destroy any pathogens in lymph
What are two sets of defence proteins?
Complement
Interferons
Examples of the first line of defence
Skin - physical barrier that prevents pathogens from passing through
Clotting - If skin is broken, blood clotting prevents entry of further pathogens [prevents blood loss]
Lysozyme - enzyme found in sweat, tears and saliva which attacks and dissolve the cell wall of many bacteria t
Sebaceous glands - in the skin produce chemicals that kill bacteria [released in sebum oil]
Mucous - pathogens trapped by mucous and prevented from entering the body
Cilia - respiratory system is lined with tiny hairs known as cilia which beat and create a current, which moves mucous back up the respiratory system so that it can be swallowed into the stomach
Acid - hydrochloric acid in the stomach kills pathogens
Beneficial bacteria - in the vagina produce lactic acid which prevents the growth of pathogens
What is complement?
It’s a set of about 20 proteins found in the blood plasma
How are the proteins in complement help the human defence system?
The proteins in complement are activated by infection, and they destroy viruses and other pathogens
What are interferons?
A set of defence proteins that prevent viral multiplication and help to limit the spread of virus infections such as colds and influenza
What is the second line of general defence?
Consists of the destruction of pathogens by white blood cells, the production of a series of proteins that kill or prevent pathogens from reproducing and the inflammatory response
What are phagocytise white blood cells
When cells are damaged by invading micro organisms they release a large number of chemicals which attract phagocytes from the bloodstream, the phagocytes engulf and destroy any micro-organisms they meet
What are macrophages?
Large phagocytes. Some move around body in body fluids and act as scavengers for pathogens whereas others remain in fixed places such as steel, lymph nodes and other lymphatic tissues, such as tonsils. They filter out and destroy any pathogens in lymph
What are two sets of defence proteins?
Complement
Interferons
What is complement?
It’s a set of about 20 proteins found in the blood plasma
How are the proteins in complement help the human defence system?
The proteins in complement are activated by infection, and they destroy viruses and other pathogens
What are interferons?
A set of defence proteins that prevent viral multiplication and help to limit the spread of virus infections such as colds and influenza [they interferreeeONSSSS]
How does inflammation help the defence systeM?
When cells are infected they release a chemical that results in blood capillaries opening wider which causes localised swelling, redness, heat and pain. This brings more white blood cells to the area to fight infection.
What occurs when inflammation occurs over the whole body?
It causes increased body temperature = fever and this interferes with the ability of some bacteria and viruses to reproduce
What is the specific defence system?
Attack particular pathogens
How does the specific defence system work?
Production of antibodies or when white blood cells destroy body cells infected by specific pathogen
Where are monocytes and lymphocytes made?
Bone marrow, they move into blood vessels and into parts of lymphatic system [lymph vessels, nodes, spleen]
What are monocytes?
They develop into macrophages. These recognise foreign molecules [antigens] that are present on the surface of pathogens. When macrophage digests a pathogen, antigens from pathogens displayed on surface of macrophage. These antigens stimulate production of antibodies
How do lymphocytes fight infection?
Some lymphocytes attack body cells that contain antigens on surface. Cells may be infected with pathogen or may be cancerous
Other lymphocytes produce antibodies
What is an antigen?
It’s a foreign molecule that stimulates the production in antibodies
What is an antibody?
It’s a protein produced by white blood cells [lymphocytes] in response to an antigen
The antigen-antibody reaction is a highly specific reaction why?
There is a precise fit between the antigen and antibody - each antigen stimulates the production of only one specific antibody
How to antibodies help dispose of pathogens?
Antibodies prevent viruses and bacteria from entering new host cells, the pathogens are then destroyed by phagocytes
Antibodies inactive pathogens by causing them to clump over her which allows the phagocytes to destroy the pathogens
Antibodies trigger the complement system with results in the pathogenic cells being burst
Why do we usually not suffer from the same infection for a second time?
Due to memory cells. After an infection is over come, some of the antibody- producing lymphocytes remain in the body for a long time. If a second similar antigen enters the body later, these memory lymphocytes can rapidly produce large amounts of a specific antibody
Why can we suffer from cold and influenza more than once?
There are many different forms of cold and flu viruses [with different antigens]
What is induced immunity?
It’s the ability to resist diseases caused by specific pathogens by the production of antibodies
What are the two types of induced immunity?
Active and passive immunity
What is active immunity?
Involves the production of a persons own antibodies in response to antigens that enter the body [long lasting bc memory cells]
What is natural active immunity?
Occurs when a pathogen enters the body in a normal way
What is artificial active immunity?
It occurs when a pathogen is medically introduced into the body dog, vaccine
What is a vaccine?
It’s a non disease-causing dose of a pathogen
What does a vaccine contain?
Pathogens that are killed or treated so that they cannot reproduce [use the outer wall of the pathogen]
What is the benefit of a vaccine?
The person produces antibodies without suffering the full symptoms of the infection
What do booster vaccinations do?
They strengthen the effect of the first treatment
What is passive immunity?
Occurs when individuals are given antibodies that were formed by another organism
How long does the passive immunity last?
Until the antibodies are broken down in the recipients body [usually between a few weeks and about 6 months]
What is natural passive immunity?
When a child gets antibodies from mother via placenta when child is in womb or in the mothers milk if the child breast feeds
What is artificial passive immunity?
Occurs when a person is given an injection containing antibodies made by another organism
Give an example of artificial passive immunity and explain it
Anti-tetanus injection. Antibodies are extracted from blood samples taken from horses that have been infected with tetanus bacteria. These antibodies are then given to an infected human
There are two types of lymphocytes, what are they?
B cells and T cells [b-lymphocytes and T-lymphocytes]
How are B cells and T cells distinguished?
According to location in which they mature
Where do B cells mature?
In the bone marrow
Where do t-cells mature?
In the thymus gland
Where do b-cells go once matured?
Move out into lymphatic tissue, especially spleen and lymph nodes
What happens when a b-cell comes into contact with the antigen to which it is targeted?
It multiplies to produce large amounts of required antibody
Most of the b-cells die off once the infection has been overcome, however some remain alive, what are these called?
Memory b-cells
The b-cells secondary response is much more effective, why?
Three factors that prevent us from being infected more than once by same pathogen
Memory b-cells produce antibodies in response to much smaller amounts of antigen
It produces antibodies much faster
It produces much greater numbers of antibodies than is the case with a first time infection
Role of helper t-cells
Stimulate production of the correct b-cells
Activate killer T cells
Role of killer t-cells
Attack infected cells
Release perforin [protein]
Role of surpressor t-cells?
Inhibit b-cells, other t-cells + macrophages and this way turn off the immune response when infection is over
What do memory t-cells do?
Can survive for a long time so if a pathogen re enters a persons body, the memory t-cells rapidly stimulate memory b-cells to produce large amounts of correct antibody
Also trigger production of killer t-cells
An outbreak of measles occurred in Ireland, name a group of people who would be most at risk?
Non-vaccinated
How does a vaccine result in immunity?
It produces antibodies which stay in body and produce long term immunity
What is asepsis?
Free of pathogens
Outline how any one named feature of the human general defence system works
Skin
Physical barrier that prevents pathogens passing through
Clotting when skin breaks which prevents further entry of pathogens
Sebaceous glands in skin produce chemicals in sebum oil which kill bacteria
Name two organs in the human body that are specific to the immune system
Thymus
Spleen
Outline briefly the role of B lymphocytes in the human immune system
Recognise specific antigen and produce large amounts of antibodies in response to specific antigen and inactivates antigen
“Vaccination gives rise to active immunity” explain this statement
Vaccine is a non disease causing dose of a pathogen which stimulates production of antibodies - active immunity
Under what circumstances might an antibody, rather than a vaccination be given?
Infection may have already occurred
Comment on the duration of immunity that follows administration of an antibody
Short term
Using your knowledge of antibiotics and bacteria, suggest why a person is more likely to pick up infection in hospital than at home
More pathogens
What is the role of antibodies in the body?
React with antigens and inactivate them
Name two types of lymphocytes and state a role of each when viruses or other micro organisms enter the blood
B lymphocytes - produce antibodies in response to antigen
T lymphocytes - killer T cells destroy infected cells
“Immunity that results from vaccination is effectively the same as immunity that develops following an infection” do you agree and explain
Yes
Result of both in production of antibodies
