innate immunity Flashcards
What is innate immunity?
They start acting ______ on encounter with infectious agents.
It is the defense system with which you were born;
immediately
What immunity displays these characteristics?
- fully active w/o history of prev encounter
- generic response that targets invading pathogens
- recognise broad classes of microbes
- does not confer long-lasting immunity
Innate immunity
Innate immunity is activated by _________
conserved foreign molecules
Innate immunity involves:
- macrophages
- neutrophils
- dendritic cells
- natural killer cells
- mast cells
- basophils
- eosinophils
The 3 main components of innate immunity
- physical barrier (skin, epithelial & mucous membrane surface, mucous)
- chemical defences (Eg.lysozyme)
- phagocytes (eg. neutrophils, macrophages)
Peptides and proteins function in innate defense by _________ or ________
attacking pathogens or impeding their replication.
______ have direct bactericidal properties. (kills bacteria)
Defensins
______ is present in tears
Lysozyme
Lysozyme is found in high concs. inside ______, ______, ______
macrophage
neutrophil
dendritic cell
______ hydrolyses polysaccharide component of bacterial & yeast cell walls.
Lysozyme
Are commensal bacteria harmful?
What is their main role?
No
They play a protective role by preventing pathogen colonization & invasion
What are the other functions of commensal bacteria?
- maintain epithelial integrity
- produce bacteriocins
- compete for nutrients
What happens when a pathogen breaks through or bypasses our barrier defences?
So what must be done?
breached barriers predispose to infections (even if the patient has an intact immune system)
Need to remove foreign bodies that are foci of infection
What are pathogen associated molecular patterns (PAMPs)?
And do they evolve rapidly?
They are molecules that are associated with pathogen infection that serve as ligands for host pattern recognition molecules.
No
Example of PAMPs and where are they derived from?
1) flagellin – derived from bacteria
2) lipopolysaccharide – bacteria
3) zymosan – fungi
4) ds RNA – virus
5) profilin-like molecule– protozoa
What are pattern recognition receptors (PRRs)?
PRRs are able to distinguish between _____ and ______.
They are proteins which recognise molecules frequently found in pathogens (PAMPs) / receptor for PAMPs.
self & non-self
Types of PRRs:
- secreted
- extracellular (located on surface)
- intracellular
PRRs trigger ______.
And thus lead to the variety of processes:
They trigger the innate immune response
- opsonisation pathogen
- complement activation
- phagocytosis
- activate the inflammatory mediators (eg. IL-1β, TNF-α) & chemokines
- secrete interferons, cytokines & pro-inflammatory cytokines
- killing of infected cells by NK cells
- induce changes in expression of molecules involved in T-cell activation by APC
Example of PRRs
toll-like receptors (extracellular)
List all phagocytic cells
neutrophils
monocytes
macrophages
dendritic cells
Phagocytosis is induced upon ____________
ligation (joining) of many of the cell-surface receptors that recognise pathogens
Mannose receptor directly binds to ________________
polysaccharides on microbes
Scavenger receptors directly recognise ________________
charged molecules on targets
Fc receptors only bind _________
antibody-opsonised targets
Complement receptors only recognise ___________
complement-reacted targets
Complement definition
defense molecules
Complement is important for defending against ________ and ______.
extracellular bacteria and fungi
Functions of complement system
- opsonisation
- inflammation through recruitment & activation of immune cells
- complement-mediated cytotoxicity through the formation of membrane-attack complex
Essential roles of inflammation in combating infection
- deliver additional effector molecules and cells to site of infection to augment the killing of invading microorganisms by macrophages
- prevent the spread of infection
- promote the repair of impaired tissue
The inflammatory response involves 3 major stages:
1. _________ to increase blood flow
- microvascular structural changes & _________ from the bloodstream (_________,_________)
- __________________ through endothelium & _________ at the site of injury
- dilation of capillaries to increase blood flow
- microvascular structural changes & escape of plasma proteins from the bloodstream (antibodies, complement)
- leukocyte transmigration through endothelium & accumulation at the site of injury
Describe the process of inflammation
- tissue injury– release of _________ such as _________
- these chemicals cause blood vessels to _________ into tissues, causing _________
- the chemicals also attract _________, then _________ occurs
- tissue injury– release of chemical signals such as histamine
- these chemicals cause blood vessels to leak fluid into tissues, causing swelling
- the chemicals also attract phagocytes , then phagocytosis occurs
Fever is a common response to infection:
- inhibits ____________
- increases _____________ & stimulates_____________
- inhibits multiplication of sensitive microbes
- increases host metabolism & stimulates immune activity eg phagocytosis
C-reactive proteins (CRP) are synthesised by the _____ in response to inflammatory cytokines, especially _______.
liver;
IL-6 and TNF
Lab tests of __________:
- CRP
- procalcitonin
- erythrocyte sedimentation rate
acute phase response
Type 1 interferons are ______ which can be produced by __________ in response to viral infections.
Examples of type 1 interferons:
cytokines;
almost all nucleated cells
examples: IFN-α & IFN-β
Natural killer cells are activated by _____ and _____ including ____ and ____.
activated by interferons & macrophages/dendritic cell-derived cytokines including TNFα & IL-12
Dendritic cells present antigens to _____. Small no. of dendritic cells activate large no. of _____ (both same ans)
T cells
- _____ dendritic cells migrate through the lymphatic system towards lymph nodes, where they 2. ________ of the material pathogen antigens to T cells and in so doing stimulate 3. _________.
- mature
- present fragments
- adaptive immune response
TNF alpha & IL-12 activate ________
NK cells
