Blood and Immune [Infection & Innate Immunity] Flashcards
3 processes of innate immunity
- Complement
- Myeloid cells and phagocytosis
- Pattern recognition receptors (PRR) which are found on myeloid cells.
Bacteria
Extracellular pathogens (mostly). Defense through innate mechanisms and phagocytosis. Distinguished by the gram stain.
Protozoa and Parasites
Complex multicellular organisms (worms).
Too big to be engulfed so myeloid cells must secrete inflammatory mediators (degranulation) and granules filled with cytotoxic chemicals that kill.
Bacteria: Gram positive
Thick peptidoglycan cell wall. Requires phagocytosis and not killed by complement.
Bacteria: gram negative bacteria
Thin peptidoglycan layer surrounded by outer membrane. Can be lysed by complement.
Neutrophil Extravasation: Activation
Chemokines from the site activate local endothelial cells lining adjacent capillary wall.
Neutrophil Extravasation: Tethering
Neutrophil tethers to the inside capillary wall. Mediated by selecting upregulated on endothelial cells and sialyl Lewis X, a carbohydrate antigen on neutrophils.
Neutrophil Extravasation: Adhesion
Strong binding between neutrophil intestine and ICAM-1 on the endothelium. Neutrophil immobilised and flattens.
Neutrophil Extravasation: Diapadesis
Neutrophil squeezes between endothelial cells and out of the capillary into the interstitial space (tissue).
Neutrophil Extravasation: Chemotaxis
Neutrophil migrates along a chemical gradient to the site of infection.
Phagocytosis: ingestion
The bacterium is captured by receptors, membrane invaginates into a phagosome.
Phagocytosis: Digestion
Acidification activates protease and stimulates the production of superoxide which kill bacteria.
Acronym for phagocytosis steps
I FADE
What are TLR’s?
Toll-Like Receptors: PRRs - bind complex molecules unique to microbes. Look like a slinky.
Activation through TLR activates a strong innate response through an inflammatory pathway.
What are PAMPs?
Pathogen Associated Molecular Patterns.
Molecules unique to microbes. Recognised by PRRs.
Complex and stable. Stimulate power switch for adaptive response.