Immune Response to Bacteria Flashcards
What is the response time of innate immunity?
Rapid (hours)
What is the specificity of innate immunity?
Relatively non-specific (looks for basic patterns)
What is the memory of innate immunity?
No memory
What is innate immunity particularly important for?
Our response against bacterial pathogens
What does innate immunity deal with?
The early stages of microbial pathogenesis (adherence, invasion, replication)
Where are the physical and chemical barriers to bacterial attachment and invasion found?
Skin, airways and gut
What physical and chemical barriers are found in the skin?
Dead cells and keratin, sebum (trapping and pH) and salt (osmotic control)
What physical and chemical barriers are found in the airways?
Mucus (trapping) and beating cilia moves bacteria up to the throat where they are swallowed or removed
What physical and chemical barriers are present in the gut?
Constant flow of fluids (especially if gut inflammation results in diarrhoea) prevents bacteria from attaching itself, stomach acid, digestive enzymes (pancreas) and bile (gall bladder)
What are AMP’s?
Antimicrobial Peptides
What is an example of an AMP?
Defensins
Where are defensins produced?
In the skin, airways and gut
What do defensins do?
Charged defensins preferentially bind to the bacterial cell membrane which is charged unlike plant and mammal cell membranes
What do defensins do once bound?
Disrupt the normal function of gram negative and gram positive cell membranes by interacting with proteins and pumps which are embedded in those membranes
Where are lysozyme produced?
In the skin and airways
What is lysozyme especially effective against?
Gram positive bacteris
What does lysozyme do?
Breaks the bonds between the glycopeptides (NAM and NAG) in the sugar layers of the cell wall
What happens first if bacteria make it past the first defence?
Leukocytosis
What is leukocytosis?
Neutrophils enter the blood from the bone marrow
What happens after leukocytosis?
Margination
What is margination?
Neutrophils cling to capillary cell wall
What happens after margination?
Diapedesis
What is diapedesis?
Neutrophils flatten and squeeze out of capillaries
What happens after diapedesis?
Chemotaxis
What is chemotaxis?
Neutrophils follow chemical trail
What are the 3 pathways of activating complement?
Alternative, classical and lectin
What are the innate ways of activating complement?
Alternative and lectin pathways
What is involved in the alternative pathway?
Molecules on the outside of the bacteria activate complement
What happens in the lectin pathway?
Mannose (particularly found in fungi and not produced naturally by humans) binding lectin
What are the possible outcomes of the complement cascade?
Label, destroy and recruit
What happens in label?
Opsonisation (labels pathogens which bind to complement receptors on phagocytes)
What is opsonisation?
Coating of a microbe with antibody and/or complement fragment C3b
What complement protein is linked to labelling?
C3b
What happens in destroy?
Membrane attack complex formation (pores in bacterial cell all»_space;> death)
What happens before MAC forms?
Microbes coated with C3b are phagocytosed and then assembly of MAC causes lysis
What complement protein is linked to destroying?
C9
What happens in recruit?
Complement proteins act as peptide mediators of inflammation and recruit phagocytes
What complement protein is linked to recruit?
C3a and C5a
