Infection and innate immunity Flashcards
What is innate immunity
all living things are able to discriminate between self and non-self
Describe innate immunity
provides first line or immediate response to pathogen invasion
more primordial than adaptive immunity
has no memory. It is what you are born with
What are the 3 main types of pathogens
Viruses: intracellular pathogens
Bacteria: extracellular P
Protozoa and parasites
Describe Viruses: Intracellular pathogens
defense relies on antibodies and cellular immunity- need to be able to distinguish infected from normal cells
eg. Influenza/ polio
Describe Bacteria: extracellular pathogens
defense is primarily mediated by innate mechanisms and phagocytosis
what are examples of a viruses: Intracellular pathogen
eg. Influenza/ polio, small pox
examples of bacteria: extracellular pathogens
Black plague
rheumatic fever
Cholerae
Describe Protozoa and parasites
complex multicellular organisms require direct killing by chemical mediators released by specialist myeloid cells
What are Granules involvement with Protozoa and Parasites
Granules filled with cytotoxic chemicals. Degranulation releases these toxic inflammatory chemicals such as histamine
Describe Neutrophil extravasation steps
- Activation. Chemokines
- Tethering
- Adhesion
- Diapadesis
- Chemotaxis
Describe Neutrophil extravasation
Activation step
Chemokines from tissue injury or inflammation activate the local endothelial cells lining an adjacent capillary wall
Describe Neutrophil extravasation
Tethering step
Neutrophil tethers to the inside capillary wall. mediated by selectins upregulate on endothelial cells and sialyl Lewis X
What is sialyl Lewis X
a carbohydrate antigen on neutrophils
Describe Neutrophil extravasation
Adhesion step
strong binding between neutrophil integrins and ICAM-1 on the endothelium.
Neutrophil immobilizes and flattens
Describe Neutrophil extravasation
Diapadesis step
neutrophils squeeze between endothelial cells into the interstitial space
Describe Neutrophil extravasation
Chemotaxis step
Neutrophils migrate along a chemical gradient to the site of the infection
what is a FcR
an Antibody
Describe the FcR antibody mediated phagocytosis
- Antibody (IgM and IgG) bind to bacterial antigens
- Exposes the antibody Fc region
- Neutrophil FcR binds multivalent Fc
- Activates phagocytosis
- Membrane invaginates forming phagosome
- fuses with lysosome to form phagolysosome
- Phagolysosome acidifies and superoxide’s kill bacteria
What are PAMPS
Pathogen Associated Molecular Patterns
Describe PAMPS
Molecules unique to microbes recognised by Pattern recognised receptors
Describe PAMPS structures
structurally very complex eg. lipopolysaccharides
evolutionarily stable- dont change much
stimulate the power switch for the adaptive response
Describe Toll- Like receptors (TLR)
- Molecular pattern recognition.
Pattern recognition receptors (PRR) bind complex molecules that are unique to microbes
best known are the Toll- like receptors (TLR).
Activation of the TLR stimulates a strong innate response through an important inflammation pathway.
Describe the receptor for lipopolysaccharides (LPS)
LPS is a membrane component of all gram negative bacteria
tiny amounts induce a powerful innate response
LPS is a pyrogen- raises temp. It causes fever when injected into the bloodstream
What occurs with the release of LPS
released by Gram negative bacterial infections lead to Septic Shock
Describe Complement receptors CR1, CR2, CR3, CR4
Myeloid cells receptors that bind activated complement components deposited on bacteria
CR1 is the main neutrophil receptor and binds to C3b
cross linking of the surface CRs initiates phagocytosis
