OVERVIEW (CHP 24)
The functions of the immune system include:
1. Tries to recognize and remove abnormal “self” cells
2. Removes dead or damaged cells
3. It protects the body from disease-causing invaders.
Failures of the immune system include:
1. Incorrect responses (autoimmune diseases)
2. Overactive responses (allergies)
3. Lack of responses (immunodeficiency disease)
a. Primary immunodeficiency – genetically inherited immunodeficiency
b. Acquired immunodeficiency – acquired as a result of a virus or treatment
PATHOGENS (CHP 24)
Bacteria and viruses differ in a number of ways.
1. Structure:
a. Bacteria are cells, with a cell membrane and often a cell wall. Encapsulated bacteria have a
capsule.
b. Viruses are not cells. They are a ball of nucleic acid (DNA or RNA) enclosed ina coat of viral
proteins called a capsid.
2. Living conditions and reproduction.
a. Bacteria can survive and reproduce outside of a host (wtih required nutrients)
b. Viruses must use the intracellular machinery of the host cell to replicate.
3. Susceptibility to drugs.
a. Bacteria can be killed by antibiotics
b. Viruses cannot be killed by antibiotics, some can be killed by antiviral drugs.
Viral Replication
1. The virus enters the host cell via receptor mediated endocytosis or fusion with the membrane.
2. Within the cell, the virus overtakes the host cell resources for nucleic acid replication.
3. These components are assembled into additional viral particles which infect other cells.
4. Viruses are released from the cells. Possible in two ways…
a. The virus induces host cell rupture.
b. Virus surrounds itself in host cell membrane and buds off cell surface.
, THE IMMUNE RESPONSE (CHP 24)
The body has two lines of defense:
1. Physical and chemical barriers.
2. Internal immune response.
The internal immune response has four basic steps.
1. Detection and identification of a pathogen.
2. Communication with other immune cells.
3. Recruitment of assistance and coordination of the response among all participants.
4. Destruction or suppression of the invader.
The immune response is distinguishable from other responses.systems by its extensive use of chemical
signalling.
- Cytokines are protein messengers released by one cell to affect the growth or activity of another.
- Antibodies are proteins secreted by certain immune cells, that bind antigens and make them visible
to the immune system
The immune system can be divided into two
subsystems:
1. The innate (non-specific) immune system:
Defense mechanisms present from birth
a. Broad specificity receptors, specific to
patterns common in pathogens.
b. Inflammation is a hallmark of innate
immunity.
2. The acquired (specific) immune system:
Defence mechanisms acquired as a result of
previous confrontation with a non-self
molecule.
a. High specific receptors, receptors distinguishable between targeted pathogen.
b. Cell-mediated immunity: contact dependent signalling to carry out immune response.
c. Humoral immunity (antibody mediated): antibody dependent signalling to carry out immune
response.
- The innate response occurs first, but the acquired immune response, once developed is stronger,
more specific and very rapid.
The functions of the immune system include:
1. Tries to recognize and remove abnormal “self” cells
2. Removes dead or damaged cells
3. It protects the body from disease-causing invaders.
Failures of the immune system include:
1. Incorrect responses (autoimmune diseases)
2. Overactive responses (allergies)
3. Lack of responses (immunodeficiency disease)
a. Primary immunodeficiency – genetically inherited immunodeficiency
b. Acquired immunodeficiency – acquired as a result of a virus or treatment
PATHOGENS (CHP 24)
Bacteria and viruses differ in a number of ways.
1. Structure:
a. Bacteria are cells, with a cell membrane and often a cell wall. Encapsulated bacteria have a
capsule.
b. Viruses are not cells. They are a ball of nucleic acid (DNA or RNA) enclosed ina coat of viral
proteins called a capsid.
2. Living conditions and reproduction.
a. Bacteria can survive and reproduce outside of a host (wtih required nutrients)
b. Viruses must use the intracellular machinery of the host cell to replicate.
3. Susceptibility to drugs.
a. Bacteria can be killed by antibiotics
b. Viruses cannot be killed by antibiotics, some can be killed by antiviral drugs.
Viral Replication
1. The virus enters the host cell via receptor mediated endocytosis or fusion with the membrane.
2. Within the cell, the virus overtakes the host cell resources for nucleic acid replication.
3. These components are assembled into additional viral particles which infect other cells.
4. Viruses are released from the cells. Possible in two ways…
a. The virus induces host cell rupture.
b. Virus surrounds itself in host cell membrane and buds off cell surface.
, THE IMMUNE RESPONSE (CHP 24)
The body has two lines of defense:
1. Physical and chemical barriers.
2. Internal immune response.
The internal immune response has four basic steps.
1. Detection and identification of a pathogen.
2. Communication with other immune cells.
3. Recruitment of assistance and coordination of the response among all participants.
4. Destruction or suppression of the invader.
The immune response is distinguishable from other responses.systems by its extensive use of chemical
signalling.
- Cytokines are protein messengers released by one cell to affect the growth or activity of another.
- Antibodies are proteins secreted by certain immune cells, that bind antigens and make them visible
to the immune system
The immune system can be divided into two
subsystems:
1. The innate (non-specific) immune system:
Defense mechanisms present from birth
a. Broad specificity receptors, specific to
patterns common in pathogens.
b. Inflammation is a hallmark of innate
immunity.
2. The acquired (specific) immune system:
Defence mechanisms acquired as a result of
previous confrontation with a non-self
molecule.
a. High specific receptors, receptors distinguishable between targeted pathogen.
b. Cell-mediated immunity: contact dependent signalling to carry out immune response.
c. Humoral immunity (antibody mediated): antibody dependent signalling to carry out immune
response.
- The innate response occurs first, but the acquired immune response, once developed is stronger,
more specific and very rapid.
