Foundations in Immunology 1 Flashcards
Tolerance
Immunological unresponsiveness to an antigen
How is self-tolerance maintained?
- The elimination of lymphocytes which react to self-antigens in their early stages of development
- Allowing lymphocytes to encounter self antigens in a setting which leads to their destruction if they react to self-antigens
What does the body’s immune defences not usually attack?
Tissues that carry a self marker.
Pathogen
Any organism that cause harm
What organisms can cause harm?
- Viruses
- Protozoa
- Bacteria
- Fungi
- Parasite
What physical barriers do our bodies have?
- Skin
- Reproductory, respiratory and digestive tracts
What is the main barrier to infection?
Mucous membranes
What does mucus prevent?
The attachment of pathogens and any pathogens that are trapped are repeatedly sloughed off
What produces mucus?
Goblet cells
What does mucus contain?
Antimicrobial enzymes such as growth inhibitors, enzyme inhibitors, lysins and immunoglobulins.
What do lysins do?
Kill invading pathogens
What do immunoglobulins do/
Help destroy pathogens
What are the two divisions in the immune system?
- The innate immune system
- The adaptive immune system
What are the characteristics of the innate immune system?
- Non-specific
- First to come into play
- Will produce the same response time and again=no memory
What are the characteristics of the adaptive immune system?
- Highly specific
- Immunological memory
- Antibody production
What immune system do we have when we are born?
The innate immune system
Describe the process when you receive a wound that gets infected with bacteria.
- Area around wound gets red and swollen
- Influx of macrophages to the area
What cells are professional phagocytes?
- Monocytes
- Macrophages
- Granulocytes
- Dendritic cells
Describe the process of phagocytosis.
- Chemotaxis and adherence of microbe phagocyte
- Ingestion of microbe by phagocyte
- Formation of phagosome
- Fusion of the phagosome with a lysosome to form a phagolysosome
- Digestion of ingested microbe by enzymes
- Formation of residual body containing indigestible material
- Discharges of waste materials
Describe how macrophages descend from self-renewing stem cells.
One of the daughter cells goes back to being a stem cell and the other goes through a number of choices to end up being one of a number of blood cells
Where are macrophages made?
Bone marrow
What are monocytes?
Immature macrophages that divide and differentiate to become macrophages
What causes redness in injury?
Macrophages give off chemicals that restrict blood flow away from the site of injury
What causes swelling in injury?
Contraction of endothelial cells
What do macrophages produce?
Cytokines to alert other cells to the danger and induce them to travel to the site of injury
What is the most abundant WBC?
Neutrophils
How do macrophages and neutrophils differ?
Neutrophils aren’t APCs they just eat pathogens
When do neutrophils become active?
When the enter the tissues from the blood
When do neutrophils migrate to the tissues?
In the acute phase of inflammation
What infections are eosinophils found in?
Parasitic
What are eosinophils involved in
Allergy and asthma
What do granules of eosinophils contain?
Many enzymes such as:
- Peroxidase
- RNase
- DNase
- Lipase
- Plasminogen
- major basic protein
What are mediator released by eosinophils toxic to?
Host and parasites
Where are eosinophils found?
- Thymus
- Lower GIT
- Ovary
- Uterus
- Spleen
- Lymph nodes
Where are eosinophils not found?
- Lung
- Skin
- Oesophagus
What is the cause of anaphylactic shock?
Mast cell degranulation
What do mast cells protect against?
Parasites
What do mast cells contain?
Granules containing pharmacologically active chemicals including histamine
What do mast cells do on encountering a parasite?
Dumps all of its contents onto the parasite to kill it
What happens to some people on first exposure to an allergen?
- They make lots of IgE antibodies against the allergen.
- The mast cells have receptors which can bind to the Fc region of the IgE antibodies.
What happens to some people on second exposure to an allergen?
- The IgE antibdoies which are bound to the mast cell can also bind to the allergen.
- The mast cell receptors are dragged together and a signal is sent to release the cells chemicals
What is the result of mast cell chemical release?
Increase in capillary permeability allows fluid to escape the blood vessel resulting in classic allergy symptoms
How does allergy become anaphylaxis?
- If the toxins released by mast cells spread throughout the body a massive mast cell degranulation is triggered.
- Blood volume is reduced causing cardiac arrest
- Histamine causes airway constriction
When are basophils often seen?
In parasitic infection
Describe the structure of basophils.
- Contains nucleus with two lobes
- Contains cytoplasmic granules which contain histamine
When is histamine released from basophils?
When the cell is stimulated
What are examples of non-specific humoral factors?
- Growth inhibitors
- Enzyme inhibitors
- Lysins
- Complement proteins
What does the complement system do?
Bridges a gap between the adaptive and innate immunity
What does the complement system consist of?
Serum and cell surface proteins
What is the outcome of the complement system?
Lysis of the target cell and/or opsonisation of pathogens
What are the 3 pathways of the complement system?
- Classical
- Alternative
- Lectin
How does the complement system kill pathogens?
- Proteins act together in an enzyme cascade to form a membrane attack complex making a hole in the pathogen
- This disrupts the pathogens homeostasis and it dies
What are lectins?
Sugar binding proteins that are specific for their sugar moieties
What is the central event in complement activation?
The proteolysis of complement protein C3
What pathways are effector mechanisms of the innate immune system?
- Alternative
- Lectin
What pathway is the effect mechanism of the adaptive immune system?
Classical
What is the end product of all 3 pathways?
C5 convertase
When does the membrane attack complex become active?
Once the final protein C9 is bound
What mechanisms are in place to ensure the complement doesn’t attack our cells.
- Decay acceleration factor is found on the surface of our cells and accelerates the breakdown of C3bBb
- C3b can be made inactive by proteins in the blood
What are the other functions of the complement system?
- Opsonisation of invaders
- C3a and C5a serve as chemoattractants
- Induce lysis of microbes
- Promote phagocytosis of microbes
- Stimulate inflammation
- Stimulate activation of B cells and Ab production
What can NK cells kill?
- Tumour cells
- Virus infected cells
- Bacteria
- Parasites
- Fungi
How do NK cells kill?
- They can bore holes in target cells be secreting perforin and forming a MAC.They can then secrete enzymes in via the pore and the cells commit suicide
- They contain protein FasL which interacts with Fas on the target cell surface. When they connect a signal is given and the target cell commits suicide
How can NK cells be activated?
By IFN-a and B given off by cells under viral attack
What are cytokines?
Chemicals used by cells to communicate with other cells
What signals can shift macrophages and NK cells to a higher state of activation?
LPS
What accelerators do macrophages produce?
IL-12 and TNF
What do NK cells produce in response to IL-12 and TNF?
-IFN-y
What is the inflammatory response?
The battle that macrophages, neutrophils and other immune system cells wage against an invader
What is acute inflammation?
The initial response of the body to harmful stimuli
What is chronic inflammation?
It leads to a progressive shift in the type of cells present at the site of inflammation and is characterised by simultaneous destruction and healing of the tissue from the inflammatory response.
