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
In what two ways can leukocytes me classified?
granulocytes
agranulocytes
What are the 3 granulocytes?
- eosinophils
- basophils and mast cells
- neutrophils
What are the 3 agranulocytes?
- monocytes and macrophages
- lymphocytes
- dendritic cells
What is the activated function of macrophage?
Phagocytosis and activation of bactericidal mechanisms
Antigen presentation
What is the activated function of dendritic cells?
Antigen uptake in peripheral sites
Antigen presentation
What is the activated function of neutrophils?
Phagocytosis and activation of bacterial mechanisms
What is the activated function of mast cells?
release of granules containing histamine and active agents
What is the activated function of eosinophils?
killing of antibody coated parasites
What is the activated function of basophils?
unknown
Which is the most and least abundant type of leukocyte in the blood?
Neutrophils
Basophils
What is the activated function of natural killer cells?
Release lytic granules that kill some virus-infected cells
Do most pathogens enter the body?
No, they are kept out by surface tissues and their secretions
What is the difference between the phagocytosis of pathogens with and without capsules?
Pathogens without capsules are detected by the membrane receptors of phagocytes - the membrane receptors bind to the pathogen and the pathogen is engulfed.
Pathogens with capsules: antibodies bind to the capsule of the pathogen, which then enables the antibody receptors on the phagocyte’s membrane to bind to the pathogen and engulf it
What are ingested pathogens killed by inside of macrophages?
lysosomal enzymes: lysosome (containing enzymes and oxidants) fuses with the phagosome (containing ingested pathogen), digesting and killing it
How do dendrite cells (and other antigen presenting cells) initiate adaptive immunity?
Immature dendritic cells migrate from peripheral tissues to regional lymph nodes via the lymphatic vessels. Once in the lymph node, the mature dendritic cells activate T cells
What is an antigen?
a toxin or other foreign response that induces an immune response in the body
How do macrophages develop memory?
After they have digested an antigen in lysosome, they then display antigen fragments on their surface receptors so they can react faster upon subsequent exposure
What do Natural Killer cells kill and how?
They kill infected cells by inducing apoptosis (death of cells that occurs as a normal and controlled part of their development) and some tutor cells
What 3 things do NK cells secrete?
Chemical signals called interferons.
- Interferon-alpha: prevent viral replication
- interferon-beta: prevent vial replication
- Interferon-gamma: activates macrophages and other immune cells
What stimulates inflammation?
infection or tissue damage
What are 3 beneficial roles of inflammation?
- Attract immune cells and chemical mediators to sites of infection
- Create physical barriers to prevent infections from spreading
- promote tissue repair
What are the 4 steps in the inflammatory response?
- Chemical signals called cytokines are released upon tissue damage or infection
- Acute phase proteins help prevent tissue damage
- Cytokines stimulate histamine release from mast cells
- Histamine causes two local vascular changes: vasodilation which leads to heat and redness & permeability of nearby capillaries causing WBCs and plasma to move into tissue which causes deem from osmotic effects of the plasma proteins
What are cytokines?
small proteins that stimulate or inhibit many normal cell functions such as cell growth and differentiation
What releases cytokines and why?
Tissue macrophages release cytokines to stimulate inflammation
What are 3 effects of inflammation ?
- other immune cells are attracted to the site of tissue damage
- Permeability of tissue is increased
- fever
What are 3 other chemicals that cause in inflammatory response and what is their function?
- interleukins (a subset of cytokines): secreted by leukocytes to act on other leukocytes - IL-1 mediates inflammatory response and induces fever, blood vessels become more permeable to WBCs and proteins, acute phase proteins
- Bradykinin: cause pain and swelling by stimulating pain receptors; vasodilator
- complement proteins (inactive as plasma proteins): complement protein cascade produces a membrane attack complex (MAC) that inserts into forming cell membranes and results in cell lysis
How do Membrane Attack Complexes (MAC) react with pathogens?
Complement protein part of MAC insert themselves into the membrane of a pathogen creating pores. These pores allow water and ions to flow into the cell and cause the cell to swell and rupture
What are acute phase proteins?
liver proteins that act as opsonins and that enhance the inflammatory response
What are chemotaxins?
molecules that attract phagocytes to a site of infection
what are cytokines?
Proteins released by one cell that affect growth or activity of another cell
what are opsonins?
proteins that coat pathogens so phagocytes recognize and ingest them
What are pyrogens?
fever producing substances
Slide 38
17 definitions of Chemicals of the Immune System
What does an acquired immune response do?
reacts to and targets a specific foreign molecule - the presence of a foreign antigen activates several types of lymphocytes to combat an infection
What is the difference between active and passive immunity?
Active immunity: occurs when lymphocytes are exposed foreign antigens to combat an infection
Passive immunity: occurs when we receive antibodies made elsewhere
______ regulate both innate and acquired immune system responses, and also help coordinate these responses
Cytokines
What does the acquired immunity response produce upon encountering an antigen?
memory cells
Course of the adaptive HUMORAL RESPONSE: What happens after an antigen presenting phagocyte (B-cell) presents itself to a T-helper cell?
- The helper T cell gives the B cell permission to differentiate into a plasma cell
- The antigen presenting B cell is now a plasma cell and produces an antibody against against the antigen that was presented
- Some T and B cells differentiate into memory cells that respond rapidly to any secondary encounter with antigen
CELLULAR REACTION SIDE:
- T cells identify infected cells through MHC (Major Histocompatibility Complex) antigen complexes on their surface and become activated
- The he
Course of the adaptative CELLULAR RESPONSE: What happens after an antigen presenting phagocyte (B-cell) presents itself to a T-helper cell?
- T cells identify infected cells through MHC antigen complexes (Major Histocompatibility Complex) on their surface and become activated.
- The helper T cell produces cytokines that cause the activated T cell to differentiate into cytotoxic T cell which then kills the target cell
- some B cells and cytotoxic T cells become memory cells
What are the 3 types of lymphocytes?
- B lymphocytes
- T lymphocytes
- Natural Killer (NK) cells
What type of cells are B lymphocytes and what do they secrete?
Plasma cells –> secrete antibodies
What are the 4 main types of T lymphocyte cells and what do they secrete?
- Helper T cells –> secrete cytokines
- Cytotoxic T cells –> directly attack infected cell
- suppressor T cells
- Memory T cells
Are T cells part of specific or acquired immunity?
specific
T cells make up what % of circulating lymphocytes? B cells? Natural Killer cells?
80%
10-15%
5-10%
Are B cells part of specific or acquired immunity?
specific
What to B cells differentiate/change into?
plasma cells which produce and secrete antibodies
Natural Killer cells are part of specific or acquired immunity?
acquired
What are natural killer cells responsible for?
What do they attack?
Immunological surveillance
Attack foreign cells, virus-infected cells, and cancer cells
