Immunity Flashcards
What is a virus?
An infectious microbe consisting of a segment of nucleic acid (either DNA or RNA) surrounded by a protein coat. They cannot replicate independently but instead rely on a host cell. They typically insert their genetic material into the host cell and then the use the host cell machinery to replicate the virus.
What are Protozoa?
Single celled organisms
E.g. Plasmodium which causes malaria
What are Parasitic worms/Helminths?
Large microparasites that are soil transmitted and infect the GI tract. They feed on a living host to gain nourishment and protection while causing poor nutrient absorption, weakness and disease in the host.
What is different between a gram positive bacteria and a gram negative bacteria?
Gram positive- lack an outer membrane but are surrounded by layers of peptidoglycan many times thicker than is found in gram negatives
Gram negative- thin peptidoglycan cell wall which is then surrounded by an outer membrane containing lipopolysaccharide
What colours do gram positive and gram negative bacteria stain?
Positive= stains purple
Negative = red/pink
What are 3 main shapes of bacteria?
Cocci- circular
Bacilli- Rod
Spirochaetes- Helical
What do antibiotics do?
Kill or slow the growth of bacteria
Do viruses contain RNA or DNA?
They can contain either but NOT BOTH!
What can antiviral medicines do?
They can block receptors so viruses can’t bind to and enter healthy cells
Boost the immune system, helping it fight off a viral infection
Lower the viral load (amount of active virus) in the body
What causes prion diseases?
This is when proteins in the brain misfold causing symptoms.
What is meant by the following terms?
Mutualism
Commensalism
Parasitism
Mutualism (symbiosis)- Both microbe and host benefit from the association
Commensalism- Microbe benefits from the association, no harm to host
Parasitism- Host is damaged while microbe benefits.
Can UTIs spread?
No they cannot spread from person to person like an STI. They occur when bacteria on usually your own skin or rectum comes into contact with your urethra and infects your urinary tract.
When taking blood from your finger for a blood smear, should you squeeze your finger to draw blood?
No- as this dilutes the blood
What are neutrophils?
How many lobes to the Nucleus do they have?
They are part of the innate immune response. They are very toxic to bacteria and fungi. They are typically the first cell to arrive at a site of infection. They are a type of phagocyte.
They have a multilobed nucleus (usually 2-6)
What are Eosinophils?
What does the nucleus look like?
They are part of the innate immune response. They secrete a range of highly toxic proteins and free radicals that kill bacteria and parasites.
They have 2 lobes to the nucleus
What are Basophils?
Part of the innate immune response. Basophils release histamine which plays a key role in mounting an allergic response.
They have lots of granules in their cell which masks the nucleus
What is a zoonotic infection?
An infection that spreads from animals to humans
What is the major difference between bacteria and for example protozoa and fungi?
Bacteria are prokaryotes while the rest are eukaryotes
What is the transmission of mother to child called?
Vertical transmission
Which cells of the innate immune system do you usually find in the blood?
Monocytes, Natural Killer cells, Neutrophils
What is a pyrogen?
A fever inducing substance
What are physical barriers of the body?
Mucociliary escalator, Skin (including sebum- oily secretion), Lacrimal apparatus (tears), Saliva, Gastric Juice, Urine, Body temperature
What are the 3 granulocytes?
Neutrophils, Basophils and Eosinophils
What cells are part of the innate immune response?
Which are found in the blood and which in the tissues?
Blood- Neutrophils, Basophils, Eosinophils, Monocytes, Natural Killer Cells,
Tissue- Macrophages, Mast cells, Dendritic cells, NK cells
What cell is a key interface between innate and adaptative immunity?
Dendritic cell
What is meant by Opsonization?
This is the process where Opsonins (such as C3b) bind to a pathogen so that the pathogen will be engulfed by phagocytes for destruction.
What are key features of the innate immune system?
Fast and Immediate response to invasion
Non specific to pathogens.
Response is always the same (fixed)
Triggers adaptive immune response.
What are the key features of adaptative immunity?
Specific
Diversity- Always going to be a particular antibody that is specific to a pathogen.
Tolerance
Memory cells produced after fighting a pathogen successfully.
What is the clonal selection hypothesis?
A single progenitor cell gives rise to a large number of different lymphocytes.
If a lymphocyte has a specific antigen binding site to a self antigen then they will be destroyed by apoptosis and will not leave the bone marrow.
This leaves a pool of mature lymphocytes that are not specific to self antigens.
The lymphocyte that is specific to the particular pathogen causing the infection will then be cloned causing a high number of this specific type of lymphocyte.
What are the 5 types of Immunoglobulin (antibodies) classes?
IgM, IgD, IgG, IgE and IgA
What is meant by neutralization with antibodies?
This is where antibodies bind to the surface of a pathogen which prevents bacteria binding to it.
What type of lymphocyte has a CD8+ receptor? What is there role?
Cytotoxic T cells- They bring about the killing of target cells (virus infected cell)
What type of lymphocyte has a CD4 receptor?
Helper T cells- Activate B cells to secrete antibodies and Cytotoxic T cells to kill virus infected cells.
What is the complement system?
Group of plasma proteins that are produced in the liver that work together to help destroy pathogens.
What is haemostasis?
The overall process through which blood loss is prevented
What is a thrombus?
A blood clot
What layers of blood vessels contain collagen?
All of the layers below the sub endothelium (e.g. internal elastic lamina, tunica intima, tunica media and tunica adventitia)
What is primary haemostasis?
This the process by which platelets and von Willebrand factor form an initial soft clot in the wall of the blood vessel.
Collagen is exposed to the lumen of the blood vessel due to a break in the endothelium. Von Willebrand factor covers this gap by binding to the exposed collagen molecules. This induces a conformational change in the von Willebrand factor which exposes binding sites for specialised receptors on the cell surface for the platelets.
What is secondary haemostasis?
Clot stabilisation. Activation of Fibrin.
Through what receptor on platelets do they bind to von Willebrand factors?
Platelet glycoprotein receptor
What happens to platelets when they become activated?
Change shape- become stellate (exponentially increasing the surface of the platelet cell membrane).
Their cell surface becomes very negatively charged- helps reactions that happen on their surface
How do platelets become activated?
Binding to the ligand (von Willebrand factor)
From chemicals that other platelets spit out (positive feedback)- E.g. ADP and TBXA2
By enzymes (thrombin)
What is the cell based model for clot formation?
Initiation- SMALL quantities of inactivated tissue factor diffuse into the tissue fluid. Activated VIIa leads to production of Xa and then IIa.
Amplification- platelets and cofactors become activated after a rupture in the wall of a vessel. This results in larger quantities of activated clotting factor escaping out of the vessel.
Propagation- Occurs on platelets when large amounts of thrombin (activated factor 2) produced which generates large quantities of fibrin which can resist high blood pressures and form a strong clot.
What is a zymogen?
An enzyme that is produced in an inactive form to be turned on only when needed
What is an embolus?
A lump of solid matter inside a blood vessel
Where does a pulmonary embolism occur?
This is an embolus clotting in pulmonary arteries.
How does Warfarin work?
Blocks the action of recycling of vitamin K so there is less vitamin K to activate clotting factors (i.e. 7, 9, 10 and 2) which makes you more likely to bleed
What immunoglobulin is released in response to infection for each of the 5 types?
IgA= Amylase
IgD= B cells
IgE= Eosinophils
IgG= for everything else
IgM= for maintaining blood
What are PAMPs?
They are pathogen associated molecular pattern molecules and are recognized by PRRs (pathogen recognition receptors) of innate immunity and they play a key role in the initiation of the innate immune response by detecting potential harmful pathogens.
What is IgM?
1st antibody response made.
Has two antigen binding sites
Binds to B cells.
Most effective at activating the complement pathway
What is IgG?
Most abundant antibody.
Serves as an opsonin which helps phagocytes grip bacteria.
Only antibody that can cross the placenta so newborn babies have lots of IgG during the first 6 months of life
What is IgA?
Can serve as an opsonin.
Main antibody found in mucosal sites (like salvia, breast milk, tears and semen). Prevents pathogens from entering the body.
What is IgE?
Associated with allergic and anti-parasitic responses.
What is IgD?
Found on mature B cells and serves as a signal that they are ready to leave the bone marrow.
What cytokine results in the local endothelium becoming leaky?
TNFalpha
This allows neutrphils (that have been signalled by the cytokine) to pass through more easily.
