innate immunity Flashcards
What is the main features of the innate system?
first line of defense
act immediately
instructs adaptive system
clearance of dead tissues and initiation of repair
no memory (system)
What is the main features of the innate system?
first line of defense
act immediately
instructs adaptive system
clearance of dead tissues and initiation of repair
no memory (system)
What are the first barriers of defense?
anatomic and chemical barriers (usually found on skin and mucosal surfaces)
What is the complement system?
proteins that work together to opsonise microbes, promote phagocyte recruitment, and directly kill microbes
What is opsonisation?
is the process in which microorganisms is coated by serum components, thereby enhancing recognition and ingestion by phagocytic cells
What is an important opsonin?
C3b
What does the activation of the complement system release?
C3a, C5a (involved in inflammation)
What does C3a and C5a do?
attract and activate neutrophils
activate mast cells (release of histamine and leukotriene = increase vascular permeability)
What are cytokines?
any soluble protein that affects the behaviour of cells bearing appropriate receptors
What are the major granulocytes?
neutrophil
eosinophil
basophil
What are the major profession antigen-presenting cells?
macrophage
dendritic cell
What is the major characteristic of nuetrophils?
multilobed nuclei
cytoplasmic granules
What are the main functions of neutrophils?
phagocytosis,
degranulation,
release of neutrophil extracellular traps (NETs)
What are the main functions of macrophages?
phagocytosis,
antigen presentation
What are dendritic cells?
sample antigen and migrate to lymph nodes to present antigen
What are the types of dendritic cells?
conventional dendritic cells
plasmacytoid dendritic cells
follicular dendritic cells
tissue resident dendritic cells
Plasmacytoid DCs produce what major cytokine?
type I interferons (IFNs)
What do all DCs express?
class I and class II MHC molecules –> crucial for presentation of antigens
What are the major subsets of innate lymphoid cells (ILCs)?
ILC1, ILC2, ILC3
What is the activity of ILC1?
macrophage activation
What is the activity of ILC2?
mucus production
vasodilation
macrophage activation
thermoregulation
What is the activity of ILC3?
promotion of: phagocytosis; release of antimicrobial peptides; epithelial cell survival
What are the major functions of NK cells?
kill infected cells (perforin and granzymes)
secrete cytokines
antibody-dependent mediated cytotoxicity
How are pathogens recognised by immune cells?
Phagocytes recognise pathogen associated molecular patterns (PAMPS) with pattern recognition receptors (PRRs)
How do PRRs recgonise unique microbial macromolecules?
via repetitive structural proteins
What are the types of PRRs?
Toll-like receptors (TLRs)
NOD-like receptors (NLRs)
RIG-like receptors (RLRs)
C-type lectin receptors (CLRs)
Cytosolic DNA sensors (CDSs)
What are the two principle types of reactions of the innate immune system?
inflammation
antiviral defense
What triggers the reactions of the innate system?
activation of transcription factors
What induces an anti-viral state?
IFN-α and IFN-β
What are the cardinal signs of inflammation?
redness
warmth
pain
swelling
loss of function
What do macrophages release?
inflammatory mediators - TNF, IL1 and IL6
Where can inflammatory mediators act?
locally or systemically
What is the local effects of inflammatory mediators?
TNF and IL1 act on leukocytes and endothelium to induce acute inflammation
induce expression of IL6
What are the systemic effects of inflammatory mediators?
protective = induction of fever
pathologic = decreased cardiac function, shock, thrombosis and capillary leak
