Immunity
Students explain that as a response to pathogens and disease our body has an Immune System that acts to protect against foreign invaders. Students define each line of defence through its components and role in the body. This includes terms such as phagocytes, antigen, antibodies and vaccination.
Phagocytes
Phagocytosis is the process by which solid materials (such as pathogens) are ingested by a cell (i.e. cell ‘eating’ via endocytosis)
Vaccination
Injection of killed or inactivated microbes to trigger the immune system so that it produces antibodies against a particular disease
Antigen
A harmful substance which enters the body, triggers the immune system to make antibodies.
Antibodies
Protein produced by the immune system in response to the presence of an antigen.
Antibodies neutralise pathogens in a number of ways:
The immune system can be divided into three basic lines of defence against pathogenic infection:
First Line of Defense
Second Line of Defense - Non-specific immune response
Third Line of Defense - Specific immune response
Treatment of infectious diseases. Discuss use of antibiotics
Antibiotics are compounds that kill or inhibit the growth of microbes (specifically bacteria) by targeting prokaryotic metabolism
Viruses do not possess a metabolism (they are not alive) and instead take over the cellular machinery of infected host cells
Phagocytes
Phagocytosis is the process by which solid materials (such as pathogens) are ingested by a cell (i.e. cell ‘eating’ via endocytosis)
Vaccination
Injection of killed or inactivated microbes to trigger the immune system so that it produces antibodies against a particular disease
Antigen
A harmful substance which enters the body, triggers the immune system to make antibodies.
Antibodies
Protein produced by the immune system in response to the presence of an antigen.
Antibodies neutralise pathogens in a number of ways:
- They bind to pathogens and damage or destroy them.
The immune system can be divided into three basic lines of defence against pathogenic infection:
- The first line of defence against infection are the surface barriers that prevent the entry of pathogens into the body
- The second line of defence are the non-specific phagocytes
- The third line of defence are the specific lymphocytes that produce antibodies
First Line of Defense
- The primary defence against infectious disease are the surface barriers that prevent pathogens from entering the body
- These surface barriers include intact skin (protect external boundaries) and mucous membranes (protect internal boundaries)
- Both the skin and mucous membranes release chemical secretions which restrict the growth of microbes on their surfaces
- If pathogens cannot enter the host body, they cannot disrupt normal physiological functions and cause disease
Second Line of Defense - Non-specific immune response
- The second line of defence against infection are the non-specific cellular and molecular responses of the innate immune system
- These defences do not differentiate between different types of pathogen and respond the same way upon every infection
- Phagocytic cells move to infection sites and engulf foreign bodies
- Fever increases body temperatures to activate heat-shock proteins and suppress microbial growth and propagation
Third Line of Defense - Specific immune response
- The final line of defence against infection are the lymphocytes that produce antibodies to a specific antigen
- This response forms memory cells so we can have long-term immunity to a particular pathogen.
Treatment of infectious diseases. Discuss use of antibiotics
Antibiotics are compounds that kill or inhibit the growth of microbes (specifically bacteria) by targeting prokaryotic metabolism
- Metabolic features that may be targeted by antibiotics include key enzymes, 70S ribosomes and components of the cell wall
- Because eukaryotic cells do not possess these features, antibiotics will target the pathogenic bacteria and not the infected host
- Antibiotics may either kill the invading bacteria (bactericidal) or suppress its potential to reproduce (bacteriostatic)
Viruses do not possess a metabolism (they are not alive) and instead take over the cellular machinery of infected host cells
- As such, they cannot be treated with antibiotics and must instead be treated with specific antiviral agents