L3 - Immune System Overview Flashcards
What is the role of the immune system what do we want it to d and not want it to do
we want it to:
- control infections - stop various microbes
- killing tumours - tumour surveilance
- healing - closes wounds and repairs (infection or no infection)
we don’t want it to:
- immune pathology:
- reacts too strongly → damage (kills own tissues)
- makes mistakes (allergic responses)
- identifies self cells as microbes → autoimmune
- barrier to graft rejection - recognise as foreign
- metabolic diseases - mental health & obesity (lean vs diabetes have 2 types of immune bodies, treated differently)
What is the immune system
Different cell types and molecules working together in concert to form an immune response
List 4 things the immune system must be able to do:
- detect
- distinguish (good vs bad)
- respond rapidly using appropriate killing mechanism
- control strength of response
How does HIV and SCID highlight the importance of immune system
HIV - no T cells more prone to infections
SCID - defected T and B cells = die within a year
What is our first line of defence?
Skin is both a physical barrier as well as harbouring different molecules that are specialised to live on the exterior
How do pathogens penetrate the barriers
- skin breaks (wounds/burns)
- insect bites
- animal bites
- parasites burrow through skin
Describe the mucosal barrier
- designed to take up substance and let molecules past (so decides which molecules they let past)
- cilia - in lungs push mucus out
- intestine - bicarbonate soda in stomach acid keeps out bacteria
Define how innate vs adaptive recognise pathogens
Innate
- broad specificity
- recognises danger signals and tissue damage
- ready to go rapid response
- roughly tells cell type but that’s about it
Adaptive
- highly specific
- requires time to develop
- once immune adapted makes it more useful
- memory
Timeline wise how does adaptive and innate work together
Innate response provides time for adaptive to develop specificity. Once adapted, both innate and adaptive works together
Describe the effects of not having innate vs not having adaptive.
- no buffer time since no innate immunity
- no adaptive - eventually needs specifitiy if not host dies but can hold off for a while with innate
Outline the functions of innate immunity
- Senses and responds to danger signals (infection & damage)
- Always on, always ready to respond instantly
- Communicates danger to other cells of innate and adaptive immunity
- Recruits immune cells to infection site (inflammation)
- Tells adaptive immune cells when to respond
- Cellular and biochemical killing mechanisms
What are the innate killing mechanisms
- phagocytosis (macrophages & neutrophils)
- NK cells conduct killing of infected cells
- secretion of cytotoxic granules (prestored granules)
- complement proteins punch holes in bacteria
Outline adaptive immunity intro
- Adaptive immunity consists of T cells and B cells
- T and B cells can recognise a huge range of proteins and molecules (called antigens) with a high degree of specificity
- Their specificity for the pathogen makes the immune response more effective - easier to identify target
- Identifying and expanding the T and B cells that recognisethe pathogen takes time, which is why adaptive immunity is slow
- T and B cells can remember previous encounters with pathogens (immune memory).
What are the 3 types of T cells and what do they do?
- Helper T cells - tells other cells what to do, amplify immune response
- regulatory T cells = also a talker cells but tells them to turn off (counter to helper T cells), prevents autoimmune, and prevents the immune response going too overboard
- cytotoxic T cells = identifies toxic cells
B cells are very specific. Describe them and their antibodies
- antibodies are highly specific to individual pathogens
- neutralises pathogen molecules (toxins)
- mark pathogens for destruction by other immune cells (innate)
How does B cells link the innate and adaptive immune system
- mark pathogens by binding to it so the innate cells can target
- transfers specificity from adaptive cells to innate cells
Example of immune memory: describe the faroe measles outbreak
1781 - ship brought measles, 1846 - 2nd ship brings about measles
- ones that were infected in first outbreak are resistant during 2nd outbreak
- they were usually older so the theory is counterintuitive to the fact that they are older and more susceptive to infections
- long term memory of antibodies stored in body
How does immune memory enhance adaptive immunity
- specific to original pathogen
- responds faster and bigger
- combines specificity with speed due to reservoir of memory cells
How does innate and adaptive work together
- adaptive cytokines activate innate cells
- antibodies work w innate cells to kill
Innate actibates and directs adaptive immune response
What are the 2 ways immune cells communicate
Cytokines or receptor on cell surface
What are cytokines
- chemical messengers
- diff cytokines diff functions
- Allow one cell to signal many cells
- don’t need to be in contact
- cytokines work at higher temperatures aka why there is a fever when you are sick
- whisper - talk to a few cells
- shout - lots of cytokine production, could be dangerous → sepsis
Cell to cell com using receptor/ligand pairs on cell surface
- many diff receptors and ligands w diff functions
- cells have to be in direct contact with
- very precise communication
Where are the specialised sites where immune responses are co-originated, how is this communication achieved
Lymph nodes and spleen
- T cell and B cells migrate between lymph nodes
- cells accumulate during immune response to increase probability of WBC meeting eachother → swelling of lymph nodes on infection
