immune system Flashcards
4 types of defence
- Physical barriers
- Rapid, indiscriminate defences - “innate immunity”
- Slow, high targeted defence - “adaptive” immunity
- memory
Types of physical barriers and explain
Saliva - sublingual gland and submandibular and parotid gland. Contains antimicrobial proteins (e.g lactoferrin) can directly bind to and kill bacteria. Also promotes wound healing (cuts in mouth heal faster). Promotes epithelial cell repair.
Ear wax (cerumen) - traps bacteria, dust from entering ear. Contains antimicrobial properties.
Skin - specialised, it’s directly anti-microbial. At top, have commensal bacteria
Mucus - anti-microbial. Made from goblet cells. Major component is mucin (glycosylated proteins), mucin is slippy so bacteria are unable to get a foothold on tissue.
Cilia - tiny airs, have coordinated beating which shifts water and mucous and pathogens from surface of cells, allows them to be coughed up. means they dont stay at bottom of lungs forever. This is called MUCOCILARY CLEARING
Cilia are shortened by cigarette smoke.
Differnet types of innate immune system and adaptive
INNATE:
1. first line of defence
2. rapid
3. short lived
4. not antigen-specific
5. no long term memory
ADAPTIVE:
1.
2. slower
3. long-lived
4. highly antigen-sepcific
5. long term memory
different types of innate immunity
- Epithelial cell;
They form a barrier of cells and make antimicrobial peptides - they can form a pore in the bacterial cell wall. They insert themselves into this. This disrupts the osmotic balance of the bacteria so it just dies.
Innate cells: where are they made?
Primary lymphoid organs are where immune cells are generated and where they mature
Secondary lymphoid organs are where immune cells mature and where they are activated. It’s where they live
In which primary lymphoid organs does cellular immunity develop?
Thymus: site of T cell differentiation and maturation. Top of heart. Starts switching off at age 15
Bone marrow: where most immune cells are produced and where they divide.
In which secondary lymphoid organs does cellular immunity develop?
Lymph nodes: Multiplication of T and B cells in lymph nodes occurs in response to infection
Spleen: T and B cells stored here. Important for response against infection in blood stream
Peyer’s patches: good for fighting infections in small intestine
Tonsils: in throat. Has B cells, generating immune responses in nose and throat.
What are Macrophages, give 3 functions
Each organ has its own population of macrophages which are highly specialised for that organ. They have different names e.g brain = microglia, Liver = Kupffer cells.
- If a tissue is infected they rapidly phagocytose pathogens.
- They are important activators of T cells in adaptive immune system.
- Clear dead/dying cells of all kinds to prevent them sparking an immune response
Monocytes
Circulate in the blood. Large.
Released from bone marrow and then move into tissues where they can differentiate into dendritic cells or macrophages.
Before they mature, they can phagocytose, can kill bacterial cells directly.
They produce lots of cytokines (especially TNF and IL-12 which activate other cells)
Cytokines
Signaling molecules released by immune cells. They’re small peptides.
They don’t enter cells, they bind to receptors on other cells.
Attracts the migration of other cells (saying where an infection is) - known as chemokines
What is phagocytosis and how does it happen
Ingestion of particles larger than 0.6MicroMolar (microns). often bacteria but can be dead cells.
Macrophages make pseudopodia where:
1. bacteria become attached to it
2. then, bacteria is ingested, forming phagosome
3. phagosome fuses with lysosome
4. lysosomal enzymes digest captured material
5. digestion products are released from the cell
How does the macrophage know to swallow a bacterium and not something harmless?
recognises what is dangerous by the presence of DAMPs (Damage Associated Molecular Patterns) and PAMPs (Pathogen Associated Molecular Patterns)
DAMP - these are things that are released from host cells (either as they die or under stress like hypoxia). These trigger a sterile inflammatory response.
PAMP- Come from microorangisms (e.g LPS from the wall of gram-negative bacteria)
What are neutrophils and how do they respond to infection?
Most abundant leukocyte in human blood.
Their role is to move around in large numbers be the first responder to injury or infection. They respond in 3 ways: phagocytoses, degranulation, NETosis
Degranulation: granuels in cytoplasm that are stored with anti-microbial peptides. They release these directly onto the bacteria.
NETosis: they make nets and shoot out their DNA (like spiderman) and it sticks to all the bacteria around it. They also have antimicrobial peptides so if anything gets stuck onto it it gets killed.
What are eosinophils/basophils
Granulocytes.
release of granuels allow killing of parasites. They also use their DNA to trap parasites
They make reactive oxygen species and release enzymes to break parasites down.
Key in response to large parasites.
HOWEVER they kill ANYTHING they come in contact with so this is a major trigger of asthma
What are natural killer cells?
Directly “cytotoxic cells”
Important in killing virally infected and tumour cells. They produce large amount of cytokines (e.g pro-inflammatory cytokine IFN-y)
They are lymphoid cells like T and B cells
NK cells kill cells which DON’T have the self protein MHC on their surface. This can kill all non-self cells. it does this using granules.
(btw all ur cells on ur body have the protein MHC on it so if it sees one that doesn’t then it’ll be like “omg ure not from this body get out of here”)
2 proteins in an NK cell: perforin and granzyme. If it senses a viral cell or smth then all the granules go towards the end point of the cell (this is called SECRETORY GRANUELE TRAFFICKING). They then burst out.
Perforin can form into a tube to make a hole in the viral cell. granzyme comes in after this and induces apoptosis.
