Disease And Immunity Flashcards
Define disease
Condition that impairs normal functioning of an organism
What organism causes disease?
Pathogen
Types of disease causing pathogens
- Bacteria
- Viruses
- Fungi
- Protoctists
Define communicable disease
A disease that can spread between organisms
Name some disease caused by bacterium
- Tuberculosis
- Bacterial meningitis
- Ring rot
Name some diseases caused by viruses
- HIV/AIDS
- Influenza
- Tobacco mosaic virus
Name some diseases caused by fungus
- Black Sigatoka
- Ringworm
- Athletes foot
Name some diseases caused by Protoctists
- Potato/tomato late blight
- Malaria
What are the two types of transmission?
- Direct transmission
- Indirect transmission
Describe direct transmission
When a disease is transmitted directly from one organism to another
How can direct transmission occur?
- Droplet infection
- Sexual intercourse
- Directly touching an infected organism
Describe indirect transmission
When a disease is transmitted from one organism to another via an intermediate
Through what intermediates can disease be transmitted?
- Air
- Water
- Food
- Vector
What factors can impact/affect transmission
- Living conditions
- Social factors
- Climate
How can living conditions affect transmission?
Overcrowded living conditions can increase the transmission of many communicable diseases
How can social factors affect transmission?
Worse social conditions can lead to increased likelihood of disease; income, occupation, area a person lives in.
-People with limited access to good resources, education and health care may suffer more
How can climate affect transmission?
Provides optimum conditions for breeding of vector or growth of pathogen
What animal defences against pathogens are there?
- The skin
- Mucous membranes
- Blood clotting
- Inflammation
- Wound repair
- Expulsive reflexes
How does the skin protect against pathogens?
- Acts as a physical barrier, blocking pathogens from entering the body
- Acts as a chemical barrier, producing anti microbial chemicals that kill or slow down MO and can lower pH to inhibit pathogen growth
How do mucous membranes protect an organism from pathogens?
- Protect body openings exposed to environment
- Secrete mucus that traps pathogens and contains antimicrobial enzymes
How does blood clotting help defend against pathogens?
- Blood clots plug wounds to prevent pathogen entry and blood loss
- Formed by a series of chemical reactions that take place when platelets are exposed to damaged blood vessels
What is a blood clot?
A mesh of protein fibres
How does inflammation help prevent disease
- Isolate and defend against pathogens
- Damaged tissues release molecules that increase the permeability of blood vessels so they start leaking fluid into surrounding areas
- This causes swelling and helps isolate pathogen that may have entered damaged tissue
- Molecules cause vasodilation, increasing blood flow and bringing white blood cells to the area to help fight pathogens
What is the first line of secondary defence in non-specific defences?
Phagocytosis
Define antigen
- Chemical marker on the plasma membrane of cells
- Protein or glycoprotein
Define opsonins
Proteins that bind to the antigen of pathogens and then allow phagocytes to bind
- Type of antibody
- Some are not very specific so will bind to many phagocytic cells
- Role is to enhance ability of phagocytic cells to bind and engulf pathogen
Types of phagocytes
- Neutrophil
- Macrophage
Describe a neutrophil
- Most common phagocyte
- Multi lobed nucleus
- Manufactured in bone marrow
- Travel in blood and can move into tissue fluid
- Short lived but will released in large numbers as a result of infection
- Contain a large number of lysosomes
- Engulf and digest pathogens
- Usually die soon after digesting a few pathogens
- Dead neutrophils may collect in an area of infection; form pus
Describe the process of a neutrophil
- Neutrophil binds to the opsonin attached to antigen of pathogen
- Pathogen is engulfed by endocytosis forming a phagosome
- Lysosomes fuse to the phagosome and release lytic enzymes into it
- After digestion, the harmless products can be absorbed into the cell
What parts of phagosomes are specialised for function
- Receptors on plasma membrane that can bind to opsonin or specific antigen
- Lobed nucleus that allows cell to squeeze through narrow gap
- Well-developed cytoskeleton that helps the cell to change shape to engulf pathogen and to move lysosomes and vacuoles around cell
- Many lysosomes consisting of lysin
- Many mitochondria to release energy from glucose
- Lots of ribosomes to synthesise enzymes involved
Describe a macrophage
- Larger cells manufactured in bone marrow
- Travel in blood as monocytes before settling in body tissue
- Many found in lymph nodes where they mature into macrophages
Dendritic cells
- A type of macrophage
- Found in the more peripheral tissue
What is the role of a macrophage
Role in initiating the specific response to invading pathogens
- When a macrophage engulfs a pathogen it doesn’t fully digest it
- Antigens from surface of pathogen is saved and moved to special protein complex on surface of cell
- Cell now becomes antigen presenting cell
Describe an antigen presenting cell
- A cell that exposes the antigen of a pathogen on its surface so that other cells in the immune system can recognise it
- Special protein complex ensures that the antigen presenting cell is not mistaken for a foreign cell and attached by phagocytes
What does the antigen-presenting cell do when it moves around the whole body
- Comes into contact with specific cells that can activate the full immune response
- Presents to T and B lymphocytes
Role of antigen-presenting cell
To increase the chance of the antigen coming into contact with a B or T lymphocyte that will activate the full immune response - only a certain B or T will have the correct recognition site for the antigen
Clonal selection
Selection of a specific B or T that is specific to an antigen - the activation of B or T lymphocyte
Antibodies
Specific proteins released by plasma cells that can attach to pathogenic antigens
B memory cells
Cells that remain in the blood for a long time providing long term immunity
Clonal expansion
An increase in the number of cells by mitotic cell division
Interleukins
Signalling molecules that are used to communicate between different white blood cells
Plasma cells
Derived from B lymphocytes- cells that manufacture antibodies
T-helper cells
Cells that release signalling molecules to stimulate the immune response
T killer cells
Cells that attack and destroy our own body cells that are infected with a pathogen
T memory cells
Cells that remain in the blood for a long time providing long term immunity
T regulator cells
Cells that are involved with inhibiting or ending the immune response
Describe the structure of B lymphocytes and T lymphocytes
- White blood cells with large nucleus
- Specialised receptors on plasma membrane
What do antibodies do
-Neutralise the foreign antigens
What cells do T lymphocytes differentiate into
- T helper cells
- T killer cells
- T memory cells
- T regulator cells
Role of T helper cell
-To release cytokines that stimulate B cells to develop and stimulate phagocytosis by the phagocytes
Role of T killer cells
-Attack and kill host body cells that display the foreign antigens
Role T memory cells
Provide long term immunity
Role of T regulator
- Shut down the immune response after the pathogen has been successful removed
- They are also involved in preventing autoimmunity
What types of cells can B lymphocytes develop into
- Plasma cells
- B memory cells
