Topic 4: The Immune System Flashcards
What does the human immune system do? What
role does it play?
Theimmune systemis the body system that prevents and fights disease. It is made up of many organs, tissues and cells working together. -fights both infectious diseases, like measles, and non-infectious diseases, like cancer.
What is the difference between specific and non-specific defense of the body?
specific: the response will be tailored to the specific invading agent
non-specific: the response will be the SAME regardless of the TYPE of pathogen
How does the body recognise self from non-self?
Body cells have antigens recognised by the immune system, and no immune response will be mounted against these cells. Foreign invaders have antigens that the immune system does not recognise and an immune reaction will be initiated.
What is meant by non-adaptive defense?
the response will not vary in strength and type
to suit the pathogen.
What is the first line of defense
Takes place on the body surfaces to try and stop the entry of microorganisms/pathogens
Physical barrier role (1st line)
barriersstop pathogens from entering the body by blocking or trapping them.
Explain how skin barrier works
The skin is a tough, waterproof barrier that consists or keratinised cells which make the skin tight and tough.
- when skin is cut: rapid blood clotting due to platelet action which seals the wound
- secretes sweat (high salt) and antiseptic bodies which inhibit microbial growth
Other examples of first line defense
- ear wax
- mucous membranes
What is chemical barriers
barrierskill pathogens before they can enter the body.
Example of chemical barrier
Tears/Saliva/Sweat: contain LYSOZYME which are enyzmes that cause breakdown of bacterial cell wall.
- help pathogens flush pathogens out of body
- destroy or inhibit growth of microorganisms
What is microbiological barriers
the presence of natural flora found on the skin, gut, and vagina that inhibits the growth of other pathogenic bacteria
Is the second line of defense specific or non-specific? Adaptive or non-adaptive?
non-specific, non-adaptive, no memory
Example of microbiological barrier
Natural Flora - they are better suited for the environment and dont allow other pathogens to grow
eg; Yakult, yogurt
role of macrophages
Carries out phagocytosis of any foreign pathogens. It engulfs, encloses them in a vacuole and digests them with the enzymes from their lysosomes.
- puts a part of the pathogen on the surface and presents it to T-cells to activate them
Role of neutrophil
General white blood cells that carry out
phagocytosis. They are the first to the site of
infection in large numbers.
- found commonly in bloodstream and tissues
Role of Basophil
A white blood cell that secretes histamine which causes inflammation that brings more blood into the area of the infection. (blood vessels dilate, more blood flow, more WBC)
Role of Mast Cell
- fixed cells found in the blood vessels that contain large granules of histamine which they secrete when allergen in encountered
Role of Natural Killer Cells
A white blood cell that attacks and destroys any
body cell infected with viruses or cancer. It
releases toxins to destroy cause those cells membrane to burst
What happens to lymph node when infection?
it swells and hardens as the lymph cells rapidly reproduce to increase in numbers
- if a virus/bacteria comes in lymph, the WBC destroy it before it moves on, causing glands to swell
Steps of phagocytosis
- Bacterium comes in contact with neutrophil
- The cell membrane of neutrophil/macrophage engulf the bacterium
- Neutrophil/Macrophage encloses bacteria into a vacuole
- Lysosome fuses with the vacuole and releases digestives enzymes to destroy the bacterium
What are second line WBC called?
Leucocytes
3 defensive chemical molecules
- Histamine - the process of inflammation
- Interleukin - the process of fever
- Interferon - stops viruses replicating
Role of Histamine and Inflammation
- basophils/mast cells dump histamine which causes more blood flow into the area.
- this results in vasodilation (widening of capillaries) and increased permeability (leaking capillaries)
- symptoms: redness, pain, swelling
Role of interleukin and fever
when macrophages attack invaders they secrete interleukins which cause temperature to rise to slow down pathogens, making it easier for the immune system to react
- causes drowsiness making you reduce activity, and allow for more energy of immune system to fight back
- signalling molecule
Interferon and Virus attacks
- a chemical secretes by some virally infected cells, signalling cells that are not yet infected to change their surfaces to make it difficult for virus to infect them
- reduce/slow down the growth of viral pathogen
- can alert apoptosis
How is 3rd line different to 2nd and 1st line
it is specific: the response will be tailored to the specific invading agent and it is adaptive: the response varies in strength and type to suit the pathogen. forms a memory of the pathogen
Where are B and T cells made and where do they mature?
Lymphocytes = T-cells and B-cells
Created in the bone marrow
T cells mature in the: Thymus Gland
B cells mature in the: Bone Marrow
they both circulate in the blood looking for foreign antigens
What is Humoral Response
- B-cell Response
- when b-cells produce antibodies that are secreted into the blood and lymph
What is cell-mediated response?
T cells attack the cells that have antigens they recognise
Role of Helper T cells
They activate B Cells to become plasma cells make antibodies, and release lymphokines to further inflammation and phagocytosis
Role of Cytotoxic T cells
They combine with foreign antigens displayed on surfaces and release powerful chemicals that can directly kill pathogens
Role of memory T cell
remain in the blood after pathogens have been killed
- become activated and divide rapidly at the occurrence of a second infection
- quick and strong as they recognise the pathogen
What do plasma cells do?
They secrete antibodies
Role of memory B cells
may be converted to plasma cells at a later time
What do B-cells divide into
- Plasma cells
- Memory B cells
Activation steps of a B cell
The b cell recognises foreign antigens and breaks them down, leaving pieces on its surface. The activated B cell divides rapidly and creates identical copies of itself called clones.
- receives signals from Helper T-cells to reinforce activation
Then start differentiating into either plasma cells or memory b-cells . The plasma cells become antibody producing factories and release large quantities of antibodies
What are antibodies?
specific groups of proteins also called immunoglobulins that are made by plasma cells
How do antibodies inactivate a pathogen?
Agglutination - the clumping of antigens and antibodies. Immobilises them from infecting vody cells
- Promotes phagocytosis (macrophages and neutrophils)
Primary response to infection
- no memory cells so the antibodies are made slowly and not in large numbers, takes a while and you get sick
Secondary response to infection
presence of memory cells from the first infection, recognises the antigen and respond quickly to make antibodies in large numbers, you don’t get sick.
