Lecture 22 Flashcards
Innate response:
No memory, immediate response
Viruses are ____ pathogens
intracellular
Bacteria are ___ pathogens
extracellular
Protozoa and parasites
Require killing my chemical mediators released by specialist myeloid cells
Granules are
filled with toxic chemicals such as histamine, released by degranulation
Gram positive:
Thick cell wall, requires phagocytosis, and are not killed directly by complement.
Gram negative:
Thin cell wall. Can be lysed. Membrane attack complex.
Neutrophil extravasation steps:
- Activation: Chemokines activate the local endothelial cells.
- Tethering: Neutrophils tethers to the inside capillary wall.
- Adhesion: Strong binding between neutrophil integrins and ICAM-1 on the endothelium.
- Diapedesis - neutrophil squeezes between endothelial cells into the interstitial space.
- Chemotaxis - Neutrophil migrates along a chemical gradient to the site of infection.
What is sialyl Lewix X
A carbohydrate antigen on neutrophils.
Complement receptors:
C1, C2, C3, C4. Myeloid cell receptors that bind activated complement components deposited on bacteria
What is the main neutrophil receptor that binds to C3b.
C1
FcR mediated phagocytosis:
1 IgM and IgG bind to bacterial antigens.
- Exposes the antibody Fc region.
- Neutrophil FcR binds multivalent Fc
- Activates phagocytosis.
- Membrane invaginates forming a phagosome.
- Fuses with lysosome to form phagolysosome.
- Phagolysosome acidifes and superoxides kill bacteria.
What do pattern recognition receptors (PRR) do?
Bind complex molecules that are unqiue to microbes.
What is TLR?
Toll like receptors, or Leucine RIch Repeat (LRR) receptors that look like a ‘slinky’. Activation through TLR stimulates a strong innate response.
What is a PAMP?
Pathogen Associated Molecular Patterns (PAMPs). Molecules unique to microbes recognised by PRRs. They stimulate the power switch for the adaptive response.
