Immunology Flashcards
Define Pathogen
A disease-causing agent
State three factors that make something cellular
Made of cells
Able to reproduce independently
Able to undertake independent metabolic processes
State three types of cellular pathogen
Bacteria, fungi, parasites
By what process do bacteria divide?
Binary fission
State how bacterial pathogens cause disease
Bacteria release toxins.
Bacterial populations are high due to rapid reproduction by binary fission.
This increases the volume of toxin produced, which causes disease.
State how a virus causes disease
When a virus invades a host cell it damages or destroys the cell, causing disease
Explain how a virus replicates itself
The virus is engulfed into a host cell and inserts its genetic material into host cell’s DNA.
The virus uses host cell organelles to produce new protein coats (at the ribosome) and replicate genetic material.
State how fungal pathogens cause disease
Fungi cause disease by releasing enzymes which break down proteins
Define antigen
An antigen is a unique molecule or part of a molecule that initiates an immune response
State two types of non-cellular pathogen
Virus
Prion
State three types of barriers against disease
Physical
Chemical
Microbiological/Microbial
State an example of a physical barrier against disease
Intact skin, Hair, Earwax
State an example of a chemical barrier against disease
Saliva, tears, stomach acid, mucous, sweat
Describe how microbial barriers can prevent disease
non-pathogenic bacteria outcompete pathogenic bacteria for space and nutrients, preventing colonies being established in the human body
How do lysozymes in tears and saliva act as a barrier against disease?
Lysozymes are enzymes that break bacterial cell walls, so bacterial cells burst due to osmosis
Describe the function of the lymphatic system in immunology
Transport tissue fluid back to the circulatory system samples fluid for detection of pathogens and absorption of fats
Describe the function of the circulatory system in the context of immunology
Transport white blood cells around the body
State three physical barriers against disease in plants
Intact bark Thick waxy cuticle Hairs
What is the function of valves in the lymphatic system?
Prevent backflow of lymph
Where is lymph fluid sampled for detection of pathogens?
Lymph nodes
What is phagocytosis?
Process by which a phagocyte engulfs and destroys unwanted foreign material
State two types of white blood cells involved in the second line of defense
Phagocytes
Natural Killer cells
State the function of a natural killer cell
- Detect cancerous/tumour cells and virally infected cells
- They recognise non-self antigens displayed on their surface and release chemicals which destroy the defective cell
How do antibodies stop pathogens?
- Immobilise pathogens
- Agglutinate pathogens
- Flag pathogens for phagocytosis
State the function of a T helper cell
Activate B cells
Describe the role a B cell plays in an immune response
- B cells form part of the adaptive immune system
- Once activated by a T cell, a B cell divides by mitosis
- Producing B memory cells and Plasma cells
- Plasma cells produce specific and free-floating antibodies (proteins)
- B memory cells remain in circulation in case of a secondary infection of a pathogen
State the difference between a lymphocyte and a leukocyte
A Leukocyte is a general term for all white blood cells
A Lymphocyte is a specific type of white blood cell involved in the adaptive immune response (e.g. B cells & T cells)
What is passive immunity?
- A person receives antibodies from another source
- No production of antibodies by the individual
- No immunological memory
- Immediate effect
What is active immunity?
- An individual responds to an antigen and makes their own antibodies
- Immunological memory is formed as B memory cells are made
- Takes time to respond to a pathogen
Describe Naturally acquired immunity
Immunity results from direct exposure to the pathogen/disease
Describe artificially acquired immunity
Immuniy results with no direct exposure to the pathogen/disease
Explain how a vaccine provides immunity
- Vaccine containing antigen circulates in the body
- non-self antigens are recognised by T helper cells and B cells
- T helper cells activate B cells to divide by mitosis
- These divide to produce plasma cells which will produce specific free floating antibodies AS WELL AS
- B memory cells which remain in circulation
- B memory cells rapidly produce a higher concentration of antibodies if infection reoccurs
Describe how antibiotics fight infection
Antibiotics are specific chemical agents that combat bacterial infections by either:
- Killing bacteria (bacteriocidal) or
- Slowing down bacterial growth (bacteriostatic)
Describe how antivirals fight infection
Antivirals are specific chemical agents that combat viral infections only. They work by:
- Preventing viruses binding to receptors that allow them to enter cells
- Inhibit viral enzymes involved in viral replication
- Blocking transcription and translation of viral proteins
- Preventing viruses from leaving host cells
Describe aseptic technique that should be followed when plating bacteria
- Flaming the inoculation loop
- Allow inoculation loop to cool after flaming
- Disinfect desk with ethanol
- Minimise exposure to air (tape lid shut)
- Partially open lid
- Safe disposal of used equipment in sterile packaging
State two non-specific chemical agents against pathogens
- Disinfectants: Destroy pathogens on surfaces (NOT KILL)
- Antiseptics: Destroy pathogens on the body (NOT KILL)
Describe the process of 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
Define vaccine
A solution containing a dead, weakened or attenuated form of the pathogen or antigen
