Slide Set 8 - The Immune System Flashcards
What is immunity?
The body’s ability to protect itself agains infectious disease
What are the 3 components of the immune system?
- Lymphoid tissue
- Various types of immune cells
- Chemical signals that coordinate responses
What are the 4 functions of the immune system?
- Protect against pathogens (bacteria, viruses, parasites)
- Protects against foreign molecules (toxins)
- Removes dead/damaged cells
- Attempts to recognize and remove abnormal cells
What are 3 immune system disorders?
- Incorrect immune responses (autoimmune disease - ex. Type 1 Diabetes)
- Overactive immune responses (allergies)
- Lack of immune response (immunodeficiency disease - ex. AIDS)
What are the 2 lines of defence of our immune system?
- Physical barriers
2. Immune defences: innate and acquired/adaptive immunity
What are examples of physical and chemical barriers that make up the 1st lines of defence of our immune system?
Physical:
- skin
- epithelial linings
- cilia, mucus membranes
- lacrimal apparatus
- saliva
- epiglottis
Chemical:
- sebum (secreted by sebaceous glands, low pH inhibits microbial growth)
- Perspiration (flushes skin microbes, contains lysozymes)
- gastric juice (low pH, presence of enzymes)
- Urine: flushes, preventing attachment
What are 2 characteristics of innate immunity?
- Non-specific (responds to a range of signals)
2. Immediate response
Where are 3 characteristics of acquired immunity?
- Specific - attacks a specific pathogen or antigen
- Slower but stronger response
- Memory allows for fast responses upon re-exposure
What are the 4 steps in immune response?
- detection and identification of the foreign substance
- communication with other immune cells
- recruitment of other immune cells, and coordination of the response
- destruction or suppression of the invader
What is the lymphatic system? How does the immune system play a role in this system?
a vascular system that collects tissue fluid and returns it to the blood - the lymphatic fluid (called lymph) is monitored for pathogens by immune system cells as it travels
What are the two types of primary lymphoid tissues?
- bone marrow
2. thymus (produces T lymphocytes)
What are the two types of encapsulated lymphoid tissues?
- lymph nodes
2. spleen
What is an example of a diffuse lymphoid tissue?
Tonsil
What is the structure and location of the thymus gland?
2-lobed organ located in thorax just above the heart
When does the thymus reach its peak size? What happens to it afterwards as a person ages?
during adolescence, then shrinks and is replaced by adipose tissue
During development, cells that attribute what 2 characteristics are eliminated from the body?
- cells that are self reactive in the thymus
2. cells that do not react with “self” tissue
What does the thymus gland produce?
- T Lymphocytes
2. Peptides: thymosin, thymopoietin, thymulin
What is a lymphoid nodule?
loose connective tissue with densely packed lymphocytes - not surrounded by a fibrous capsule
What does the germinal centre of lymphoid nodules contain?
dividing lymphocytes
What is the size of a lymphoid nodule dependent on?
number of lymphocytes present
What is characteristic about the location of lymphoid nodules in the body? List the 3 locations
Beneath epithelial lining of organs that have direct contact to the outside world
- respiratory tract (tonsils)
- digestive tract
- urinary tract
What happens to the fluid that flows out of capillaries via capillary hydrostatic pressure?
Some of it gets reabsorbed by colloid osmotic pressure, excess fluid that is not reabsorbed and left in the tissue gets picked up by the lymphatic system (average of 3.6 L/day)
Compare the structure of bacteria and viruses
Bacteria: Cells. Usually surrounded by cell wall
Viruses: Not cells. Nucleic acid core with protein coat
Compare the living conditions of bacteria and viruses
Bacteria: most can survive and reproduce outside of a host
Viruses: Parasitic. Must have host cell to reproduce
Compare the susceptibility of bacteria and viruses to drugs
Bacteria: most can be killed or inhibited by antibiotics
Viruses: Cannot be killed by antibiotics. Some can be inhibited with an antiviral drug
What are the 4 steps of viral structure and replication?
- Viral invasion of host cell
- Synthesis of new viral nucleic acids and proteins
- Self-assembly of new viral macromolecules into new virus particles
- Virus particles released from host cell
What is an interferon?
A protein released by mammalian cells, usually in response to the entry of a virus, that has the property of inhibiting virus replication
What are the steps to interferon and antiviral protein formation during a viral infection?
- Virus infects cell
- Viral replication in cell triggers gene expression of alpha and beta interferon protein depending on the type of host cell
- The interferon protein is released from the cell, and diffuse to neighbouring uninfected cells, binding to their receptors.
- Receptor binding triggers expression of genes for anti-viral proteins (which remain inactive in the cell upon contact with virus)
- Virus arrives at this neighbouring cell and injects the cell with its double-stranded viral RNA
- Contact of the virus’s double-stranded RNA with the antiviral protein in the cytosol of this neighbouring cell activates the antiviral protein.
- The activated antiviral protein degrades the virus’s mRNA, stops viral infection, and inhibits viral protein synthesis
Function of efferent and afferent lymph vessels:
Afferent lymph vessels carry lymph into the lymph node.
Efferent lymph vessels carry lymph out of the lymph node (from here lymph may travel to another lymph node, returned to vein)
The paracortical area of a lymph node contains mainly what type of cell?
mostly T cells
The primary lymphoid follicle contains mainly what type of cell?
mostly B cells