Topic 6.3: Defence Against Infectious Disease Flashcards
Pathogens
Pathogens are disease-causing agent that disrupt the normal physiology of infected organisms
Lines of Defense
1st line of defense – Surface barriers (skin / mucus)
2nd line of defense – Innate immunity (non-specific)
3rd line of defense – Adaptive immunity (specific)
First line of defense against infectious disease
Surface barriers that function to prevent pathogenic entry
- Skin
- Mucous Membranes
Skin methods to fight against infectious diseases
1) Protects external structures by a layer of dead cells
2) Secretes enzymes and fatty acids to lower pH and inhibit bacterial growth.
Mucous Membranes
1) Protects internal structures and cavities
2) Trap pathogens (which may then be removed)
Function of clotting
Seal damaged blood vessels to prevent pathogenic entry
Coagulation cascade (Clotting process)
a) Injured cells and platelets release clotting factors
b) These factors convert prothrombin into thrombin
c) Thrombin converts fibrinogen (soluble) into fibrin (insoluble)
d) Fibrin forms a mesh of fibers that block the injured site
e) Clotting factors cause platelets to become sticky and form a clot, sealing the wound
Characteristics of innate immune responses (2)
a) Non-specific. It does not differentiate between different types of pathogens.
b) Non-adaptive. It responds to an infection the same way every time.
Function of phagocytes
Engulf and digest foreign bodies
Method used by phagocytes to fight against infectious diseases (4)
a) Phagocytes migrate via the blood to sites of infection (chemotaxis)
b) Pathogens are surrounded by extensions and are then internalized within a vesicle via phagocytosis
c) Vesicle may fuse with a lysosome to digest the pathogen
d) Fragments (antigens) are presented on the surface of the cell to active the third line of defense
Characteristics of adaptive immune responses (2)
a) Specific. It can differentiate between different types of pathogens and respond accordingly.
b) Adaptive. It produces a heightened response upon re-exposure.
Antigen definition
Substance that the body recognize as foreign and that can elicit an immune response
Antibody definition
Globular protein produced by B lymphocytes that are specific to a given antigen
Lymphocytes method used to fight against infectious diseases
a) B cells each produce one specific type of antibody
b) Macrophages present antigen fragments to helper T lymphocytes
c) TH cells release cytokines and activate the antigen specific B cells
d) The plasma cells make antibodies specific to the antigen
e) A small proportion of B cell clones differentiate into long-lasting memory B cells
Antibiotics definition
Compounds that kill or inhibit the growth of prokaryotes by targeting prokaryotic metabolism or structure
Effect of antibiotics on virus
Since viruses do not possess a metabolism, they must be treated with specific antiviral agents opposed to antibiotics
First identified antibiotic
a) Name
b) Treatment
a) Penicillin (Fleming, 1928)
b) Florey and Chain in rats
Why does strain resistance occur?
a) Bacteria mutate and resistance to an antibiotic naturally arises
b) Bacteria divide, so a resistant strain of bacteria can proliferate
c) Bacteria strains can become resistant to multiple antibiotics
Causes of strain resistance
a) Antibiotics are often over-prescribed
b) Freely available without prescription
Methods used to infect by Human Immunodeficiency Virus
a) HIV specifically targets the helper T lymphocytes which regulate the adaptive immune system
b) The virus undergoes a period of inactivity during which infected helper T cells reproduce
c) Eventually, the virus becomes active again and begins the spread, destroying the T lymphocytes
d) With a reduction in the number of helper T cells, antibodies are unable to be produced
e) When all plasma cells have been destroyed and a person’s ability to produce a specific immune response is gone, then it’s classified as AIDS
Transmission of HIV
a) Sexual contact
b) Pregnancy
c) Childbirth
d) Injection drugs
e) Blood transfusion
Lymphatic system
The lymphatic system is a secondary transport system that protects the body by producing and filtering lymph
* Lymph is a clear fluid rich in white blood cells that arises
from the drainage of interstitial fluid from the tissues
* Lymph is filtered at lymph nodes, whereby pathogens are removed and the fluid is returned to venous circulation
