Immunology Flashcards
PAMPS
Pathogen Associated Molecular Pattern Molecules - recognised by innate immune system
Neutrophil
The most abundant immune cell circulating the blood - attracted to area by a signal from infected tissue. Engulfs and destroys pathogens (phagocyte)
Macrophage
“Big Eaters” - Can migrate or reside permanently in organs and tissues - phagocytose pathogens
Dendritic cells
Populate tissues that contact the environment (skin) and stimulate adaptive immunity
Traditional Role of Immune system
mechanism to protect us from infectious diseases through recognition and elimination
Innate Barrier defenses
Solid barrier first step in preventing invasion - easy and cost effective
Mucous Membranes
Line nose, respiratory tract, reproductive tract - cannot just have a wall as we need to have transport (for nutrients and gasses)
Where are cilia and how do they assist in innate barrier defences
Line mucus membranes and beat in one direction to keep things moving and prevent colonisation.
Skin as a barrier
Covered by dead skin cells (Keratinocytes) that form waxy impenetrable layer, and a low pH - making it inhospitable.
Mucus
Thick goopy, can bind up pathogens which can be coughed up or swallowed AND creates distance between microbes and the skin layer
Lysozyme
Enzyme that digests peptidoglycan in cell walls, therefore killing cell walls and preventing infection
Where is lysozyme found
Mothers milk, tears, saliva
How does the stomach prevent infection
low pH (1.0) therefore killing many pathogens
How is the barrier defence breached
- Cut, problems with tight junctions, change in pH or temperature, loss of normal flora
Immune cells must (5 things)
- Sense Danger
- React
- Move
- Self renew
- Be everywhere
Approach to immunity that all animals shares (4)
- Barriers to prevent infection
- Barriers that also enable limited passage
- Hostile measures to eliminate the enemy
- Layered immune system
Immune system at PEACE
Low cost, easy to maintain BUT able to react quickly
Immune System at War
High energy demand, expensive to maintain, potential for damage BUT essential for survival.
5 signs of inflammation
- redness
- heat
- swelling
- pain
- loss of function
What mediates physiological changes of inflammation
Most are cause by change in blood flow - vasodilation of blood cells = hottness and redness. Blood vessels become more permeable, so fluid can leak into surrounding tissue = swelling.
Benefit of pain/loss of function
Recognise we are at war so do not use/touch injured site
How is the immune system designed to fulfil its function
- Composed of cells that move around, react to specific things, lie dormant in peace, in war they expand and take over and are very expensive
What does immunity mean in regards to an infectious disease?
Recognition of danger and WHAT TYPE of danger - different receptors drive different types of response. Virus vs bacteria vs lungs vs skin
What is the cost of immunity
Expensive - cells which change their metabolism and react QUICKLY. Reason why we get tired when you’re sick - all energy and resources are devoted to the immune system.
What are the first defences against infection?
Barrier = cheap, effective, inhospitable wall.
How does innate immune system recognise non self
Rely on traits common to groups of pathogens, known as PAMPS
How do innate cells recognise PAMPS
Highly specific receptors - such as toll-like receptors (found in most animals). Each cell has multiple identical receptors, and each cell recognises something unique.
Function of TLR
Recognise PAMPS and activate innate immune cells
what is RAG
Recombination activating Gene
What can RAG do
give the cell that expresses it the ability to rearrange its DNA under certain conditions - allowing innate cells to create unique receptors.
Difference between innate and adaptive immune system
Innate - Broad, conserced and common motifs, multiple receptors, many cells respond, fast and consistent.
Adaptive
Unique patterns, made by DNA rearrangement, immune cells express only one receptors, very few cells involved, slow and changes over time
Vertebrates vs Invertebrates immune system due to RAG
Not all animals have the RAG gene to develop adaptive immune system. Invertebrates only have the fast and responsive innate system (rely on numbers). Verterbrates combine defense with both innate and adaptive as they posses RAG and can form adaptive.
Where do all innate cells come from
Pluripotent stem cell
WHere do T cells mature
Thymus
Where do B cells mature
Bone marrow
T - cells location in health compared to illness
Most are produced during first year of life and circulate between blood and lymph node, they will recieve inflammatory signal from infected tissue that will activate them
Lymphocytes
B & T cells
What is MHC
Major Histocompatibility complex - how you know you are you.
How to T-cells recognise their target
MHC is recognised in a complex with the antigen
How does the innate system “recognize” non self?
Toll like receptors and other pattern recognition receptors (broad)
How do adaptive immune cells recgonise non-self
T-cells build unique receptor are presented with antigen form an innate cell. Test this with the MHC innate immune cells express
B-cells directly recognise antigens
How do adaptive and innate immune system work together?
you will not get a t-cell activated without the innate system involved
Phagocytes
- Macrophage
- Dendritic Cell
- Neutrophil
Phagocytosis
- Recognition and adherence
- Uptake
- Digestion killing
Granulocytes (4 of them)
- Neutrophil
- Eosinophil
- Basophil
- Mast cell
Degranulation
Activation of a granulocyte leads to degranulation
Rapid release of pre-formed mediators
Eg. Histamine, enzymes, neurotransmitters, immune factors
Has immediate effects
Immune factor secretion
Broadly called cytokines, these Immune factors are not ready-made. They alter other cells.
Interferon (IFN)
Made by virus infected cells
Interfere with viral replication
Activate NK cells, DC, and macrophages
Interleuken - 1b
Made by many innate cells during bacterial infection
Acts on blood vessels
Causes fever (certain pathogens are very heat sensitive)
Antigen-presenting cells
Dendritic cell, Macrophage.
2 steps antigen presenting cells take
Phagocytosis
- microbes are engulfed and processed, broken down into small bits that reside on plasma membrane, and complexed with MHC
Presentation
- T-cells test antigen + MHC. If recognised, T-Cell. activated
What do Natural Killer Cells use to kill
Lytic Granules
How do NK cells kill
Detect virus infected or cancer cells - putting holes in the membrane
Kill targed cell with lytic granules
Will kill cells that don’t have recognisable MHC
3 types of adaptive immune cell
B cell, Helper T cell, Cytoxic T cell
What is the function of B cells
Make antibody
What is the function of antibody
Bind to and destroy antigen
Helper T cells function
Secrete proteins to direct other cells what to do
Cytoxic T Cells function
Like NK cells - target infected or cancerous cells and kill them
What form of MHC do helper/cytoxic cells detect
MHCII = Helper
MHCI = Cytoxic
Why do Helper T-Cells only detect MHCII
Only immune antigen-presenting cells express MHCII (DC, Macrophage, B cells)
Why are Cytoxic T Cells only activated by MHCI
All cells can express MHCI and can be potential targets
Function of Antibody
Binds and neutralises pathogens and the toxins that pathogens release.
How do antibodies support innate cell functions
Antibody can help innate cells work better by coating pathogens with “red flags” for them - easier to recognise
Coat pathogen - making phagocytosis easier
- Coat virally infected cells, allowing NK cells to kill as they can now recognise
- Bind to allergens and activate mast cells to degranulate.
Why are immune cells dangerous
four things
- Damage tissue
- Kill cells
- Very Energetically expensive
- Always moving
How do immune cells “know” where to go?
Contrilled by soluble mediation (chemokine). Chemokine is produced at the site of infection, will diffuse out and form a gradient. This gradient drives immune cells from blood into tissue
How do u stop chemokine response once it’s no longer needed
Degreade the chemokine signal OR change what different cells express (the receptors)
3 phases of immune response
- Establishment of infection
- Inductive Phase
- Effector Phase
Death By Neglect
When B and T cells have no pathogen, no antigen, and no activation, the die by neglect.
Lifespan of t and b cells (5 stage)
Antigen recognition, Activation, Proliferation, effector function, death
At what stage can immune memory form
Proliferation
Why are cells preserved as memory cells during proliferation
At proliferation, you can preserve cells. Better than the original cell that started it off, more effective, and can be activated quickly.
How do secondary response differ from primary response
Faster and Greater
How does a dendritic cell activate a T helper cell and not a cytotoxic T cell?
A dendritic cell is an antigen-presenting cell, containing MHCII which is only recognised and activates helper T cells
How do immune cells move around the body in health and during an infection?
Health - Move around blood and lymph nodes
Illness - Know how to get to infection site through attraction to chemokines
What happens after an infection is cleared?
- Adaptive cells - effector cells will die due to neglect (no longer pathogens and antigen to stimulate them), leaving population of resting cells/memory cells
