Innate Immunity - Leitenberg Flashcards
defensins
a type of antimicrobial protein
- found in plants
- constitutively produced and induced upon infection
How do defensins disrupt microbial cell membranes
defensins are positively charged and insert into the negatively charged cell wall of the microbe and causes osmotic lysis
What are two sources of antimicrobial peptides
epithelial cells and neutrophils
What are the consequences of defects in antimicrobial production might be?
increased inflammation at barrier tissue sites
Complement
family of proteins produced by liver and present in high concentration in blood
What initiates the classical complement pathway?
antigen: antibody complexes
- adaptive immune response
What initiates the MB-lectin pathway?
initiated by complement binding to lectin
- mediated by protein mannose-binding lectin
What initiates the alternative pathway
negative microbial surface found on cell walls
- antibody independent
What are the three main activities of complement?
recruitment of additional inflammatory cells, opsonization of pathogens, and killing of pathogens
Opsonization
coated by complement component: C3b to make it more noticeable for destruction
What is c3b
important complement component that serves an opsonization function
What is an opsonin
a substance which promotes binding between a particle and phagocyte to facilitate phagocytosis
Recruitment of neutrophils to tissue
- proteolytic fragments of complement proteins
- attract immune cells to the site where complement fragments are being produced
- direct binding of complement mols will cause the cells to want to migrate
MAC complex
made up of C5B-C9
- forms hole through cell wall of microbe
- disrupts osmotic integrity
- causes lysis
C3a, C5a
a for cell attraction
c3b
b for binding to microbial cell walls
c5b-c9
membrane attack complex
what do macrophages and neutrophils do
stimulate phagocytosis of microbe
What are 4 innate immune cells
macrophages, dendritic cells, neutrophils, NK cells
What are receptor characteristics of innate immune cells
- specificity inherited in the genome
- expressed by all cells of a particular type
- triggers immediate response
- recognizes broad classes of pathogens
- interacts with a range of molecular structure of a given type
What are pattern recognition receptors
recognize PAMPS
- promotes phagocytosis of the microbes and triggers signal transduction pathways that regulate gene transcriptional program
What is the target of the complement proteins
microbial cell wall components
What is the target of mannose-binding lectin protein
mannose-containing microbial carbohydrates
Toll-like receptors
expressed on plasma membrane and recognize extracellular molecules as well as in endosomal compartments
What happens when TLR engage with ligands?
induces a cascade of signal transduction events
- activation of NF-kB
What happens when Nf-Kb is activated
triggers production of pro-inflammatory cytokines
- trigger cardinal signs of acute inflammation
What are pro-inflammatory cytokines
TNFalpha, IL-6, IL-1, IL-12, IFN
NOD-like receptors
- receptors that recognize microbial patterns
- triggers signal transduction cascade
- activates NF-kB and triggers production of pro-inflammatory cytokines
What mutations are associated with Crohn’s disease
loss of function mutations of NOD
Three examples of PAMPs
peptidoglycan, single stranded/double stranded RNA, mannose, lipopolysachardide
Two examples of pattern recognition receptors
TLR, NOD-like, glycan receptors
How is inflammation induced during sterile tissue injury?
receptor mediated recognition of DAMPs
- tissue damage that leads to cell necrosis
- release DAMPs that trigger inflammatory response
What are examples of DAMPs
uric acid, stress-induced proteins (heat shock proteins), nuclear proteins
What receptors can recognize DAMPs?
NOD-like receptors and TLR
Inflammasome complex
- NOD-like receptors
- can activate caspases (enzymes that cleave other proteins in the cell)
- cleaving of IL-1B
- caspase 1 cleaves IL-IB and is secreted as pro-inflammatory
What are the two regulatory points of the inflammasome
- activating caspases that cleave the proform
- pattern recognition receptors that promote increased transcription of the gene that codes for the proform of the inflammatory cytokine
Gout
inflammasome activation in response to uric acid crystals, produces inflammation