Immunology Flashcards
Define a pathogen
Disease causing agent
What makes a pathogen cellular?
Able to reproduce independently
Able to undertake independent metabolic processes
Made of cells
List the three types of cellular pathogens
Bacteria, fungi, parasites
How do bacteria reproduce?
Binary fission
How do bacteria cause disease?
Release toxins and reproduce rapidly by binary fission, increasing toxin concentration rapidly
How do fungi cause disease?
Release enzymes which break down proteins
What is an antigen?
An antigen is a unique molecule or part of a molecule that can initiate an immune response
Antigens that belong in the body are called…
Self-antigens
Antigens that initiate an immune response are called..
Non-self antigens
What is aseptic technique?
Using practices and procedures to prevent contamination from pathogens
Give examples of aseptic technique
Disinfectant of desk with ethanol
Minimal exposure to air (taping lid shut)
Partially opening lid
Seal petri dish
Safe disposal of used equipment in sterile packaging
Why does the lag phase on a bacterial growth curve occur?
Slow increase in number of bacteria due to low initial numbers of bacteria
Why does the exponential phase on a bacterial growth curve occur?
Rapid growth/doubling of population
Resources (eg space and nutrients) are NOT a limiting factor
Why does the plateau phase on a bacterial growth curve occur?
Limited resources (ie space and nutrients)
Death rates = birth rates
Why does the death phase on a bacterial growth curve occur?
↓ population numbers
Death rates > birth rates
Lack of resources eg food
Build up of toxins
Draw and label a bacterial growth curve
What makes a pathogen non-cellular?
Not made of cells
They require a host cell to reproduce
Unable to reproduce outside a cell
Unable to undertake independent metabolic processes
How do viruses cause disease?
Viruses cause disease by damaging or destroying host cells
Give two examples of a non-cellular pathogen
Virus and prions
Draw a virus
Outline the steps involved in viral replication
- Virus invades a host cell
- The host cell replicates viral genetic material in the nucleus
- New protein coats are made at the host cell ribosomes.
- New viral particles are assembled and burst out of the host cell
What is a prion?
Abnormal infectious protein
What is the first line of defence against pathogens?
Barriers
Is the first line of defence specific or non-specific?
Non-specific (it acts in the same way against all pathogens)
List the four types of physical barriers
Intact skin, mucus, hair, ear wax
How does intact skin prevent infection by pathogens?
Prevents pathogens from entering the body
How does mucus prevent infection by pathogens?
Mucus traps pathogens and then the cilia sweep the mucus and trapped pathogens out of the body
How does hair in your nostrils/ears prevent infection by pathogens?
Traps pathogens, preventing them from entering the body
How does ear wax prevent infection by pathogens?
Traps pathogens, preventing them from entering the body
What type of cells secrete mucus?
Goblet cells
What is a physical barrier?
Physical structures that prevent the pathogen from entering the body
What is a chemical barrier?
Some type of secreted chemical that helps prevent the entry of a pathogen
How does sweat prevent infection by pathogens?
Sweat contains fatty acids and salt which kill or stop the growth of bacteria
How do tears and saliva prevent infection by pathogens?
They secrete lysozymes which break bacterial cell walls, destroying them
How does the stomach prevent infection by pathogens?
It contains stomach acid (strong hydrochloric acid) which has a low pH, killing most pathogens
List the four types of chemical barriers
Sweat, saliva, tears, stomach acid
What is a microbiota barrier?
The symbiotic microbiota outcompete the pathogenic bacteria preventing the pathogens establishing colonies and causing disease
List the three types of physical barriers in plants
Intact bark, thick waxy cuticle, hairs
What type of chemical barriers do plants have?
The secretion of chemicals like toxins, odour chemicals or oils
What is the function of the circulatory system in the immune response?
Transports white blood cells around the body
What is the function of the lymphatic system in the immune response?
Transport tissue fluid back to the circulatory system and sample fluid for the detection of pathogens
What is the function of a lymph node?
Sample the lymph fluid for pathogens
What is the function of valves in the lymphatic system?
Keeps lymph moving in one direction
What is the relationship between plasma, tissue fluid and lymph?
What are the four signs and symptoms of inflammation?
Redness, heat, pain and swelling
Why is redness experienced during inflammation?
Vasodilation (the blood vessels widen)
Why is pain experienced during inflammation?
Increased permeability. The increased swelling puts pressure on the nerves
Why is heat experienced during inflammation?
Vasodilation (the blood vessels widen)
Why is swelling experienced during inflammation?
Increased permeability. The plasma leaks out of the capillaries forming excess tissue fluid
Why does increasing vasodilation and permeability help fight infections against pathogens during inflammation?
More white blood cells go to the site of infection. (vasodilation)
The white bloods cells can enter the tissue fluid to destroy the pathogens (increased permeability)
Is the second line of defence specific or non-specific?
Non-specific
What is the innate immune response?
Non-specific immune response. Includes inflammation and the use of phagocytes and natural killer cells
What is the role of a phagocyte?
Recognise, engulf and digest foreign material, such as pathogens, through phagocytosis
List the three types of phagocytes
Macrophage, dendritic cell, neutrophil
What is phagocytosis?
Process by which a phagocyte recognises, engulfs and destroys unwanted foreign material
Outline the steps involved in phagocytosis
Phagocyte engulfs pathogen forming a phagosome
Phagosome fuses with lysosome forming phagolysosome
Pathogen destroyed by digestive enzymes in lysosome
Destroyed pathogen removed from cell by exocytosis
What is the function of a natural killer cell?
Detect cancerous/tumour cells and virally infected cells by recognising the non-self antigen displayed on their surface and release chemicals which destroy the defective cell
What white blood cells are involved in the innate immune response?
Phagocytes (macrophages, dendritic cells, neutrophils) and natural killer cells
What is meant by specific?
Reacts DIFFERENTLY for each pathogen, has a memory, slower acting
What white blood cells are involved in the adaptive immune response?
B cells (lymphocytes)
Plasma cells
Memory B cells
T helper cells (lymphocytes)
Draw and label an antibody
How do antibodies help the immune response?
Immobilise pathogens: Stop viruses from invading new cells
Agglutination of pathogens: Clumping together so that pathogens can be easily phagocytosed
Flag pathogens for phagocytosis
What is the function of a T helper cell?
Activate B cells by releasing chemicals
Outline the steps involved in the adaptive immune response
T helper cells recognise non-self antigen on the pathogen, they release chemicals to activate the B cells
B cells also recognise non-self antigen of pathogen
B cells divide by mitosis into B memory cells and plasma cells
The plasma cells secrete specific and complimentary, free-floating antibodies
The B memory cells remain in circulation in case of a secondary infection
Draw a diagram showing the adaptive immune response
What is the function of a B cell?
Divide by mitosis to produce plasma cells and B memory cells
What is the function of a plasma cell?
Produce specific and complimentary, free-floating antibodies
What is the function of a B memory cell?
Remains in circulation in case of a secondary infection, where they will produce a more rapid response with a higher concentration of antibodies
Draw a graph to compare the antibody production in the primary immune response vs. the secondary immune response
Why is the secondary immune response quicker?
T helper cells dont need to activate B memory cells
What is a passive immunity?
a person receives antibodies from another source.
Compare passive and active immunity
Passive immunity has no production of antibodies by the individual, no immunological memory and is immediate in effect whereas active immunity means the individual makes antibodies, forms immunological memory and takes time to respond
What is active immunity?
when an individual responds to antigen and makes their own antibodies
What is natural immunity?
No medical intervention, occurs naturally
What is artificial immunity?
Medial intervention
How does a vaccine work?
T helper cells recognise non-self antigen on the injected vaccine pathogen/antigen, they release chemicals to activate the B cells
B cells also recognise non-self antigen of the injected vaccine pathogen/antigen
B cells divide by mitosis into B memory cells and plasma cells
The plasma cells secrete specific and complimentary, free-floating antibodies
B memory cells lead to a more rapid production and higher concentration of antibodies if infection reoccurs at a later date as they persist in circulation and provide long term immunity.
What is a disinfectant?
A non-sepcific chemical agent that destroys pathogens on surfaces
What is an antiseptic?
A non-specific chemical agent that destroys pathogens on the body
What are antibiotics?
A specific chemical agent that kill or slow down the growth of bacteria
Compare the two types of antibiotics
Bacteriostatic antibiotics slow down bacterial growth whereas bactericidal antibiotics kill bacteria.
What is a clearance zone
The area of bacteria that have been killed by the antibiotic.
What is an antiviral?
A specific chemical agent that destroys viruses
What can antiviral drugs target?
Prevent viruses binding to receptors that allow them to enter cells.
Inhibit viral enzymes involved in viral replication
Block transcription and translation of viral proteins.
Prevent viruses from leaving host cells.
What is a vaccine?
A vaccine is a solution containing a dead, weakened or attenuated form of the pathogen or antigen.
