Host Defenses - Dwinell Flashcards
What host defenses are considered:
- Immediate?
- Early?
- Late?
- Immediate: Existing physical and chemical barriers
- Skin / epithelium
- Antimicrobial enzymes
- Acid
- Microbiota
- Early: Existing innate immune cells and mediators (cytokines, complement, etc.)
- Late: Adaptive immune cell and mediator response
Describe three ways in which commensal bacteria contribute to host defenses.
- Compete for resources with more virulent organisms
- Produce bacteriosins - their own antimicrobial peptides
- Keep host’s innate immune cells in an “attentive” state
How do antimicrobial peptides (including defensins and bacteriosins) work?
Form pores in the membranes of microbes, including bacteria, protozoa, fungi, and some viruses.
(Similar to the MAC in the complement system)
What cells produce defensins?
- PMNs
- Epithelial cells
How does lactoferrin contribute to host defense?
Sequesters free iron, which bacteria need
Can also oxidize (break down) bacterial cell walls
How does Tamm-Horsfall protein (THP) contribute to host defense? Where would you find a lot of this protein?
Inhibits uropathogenic E. coli from binding to the urinary tract epithelia
Abundant in the urine!
About how long does it take from the time an enterocyte is “born” (in an intestinal crypt) to migrate to the villus apex and be discarded into the intestinal lumen?
What is this process called and how does it benefit host defense?
5-6 days
Shedding
Microorganisms inside enterocytes (virsus, intracellular bacteria, etc.) are discarded relatively quickly - limits their spread
Genetic testing of discarded, apoptotic enterocytes in the feces is useful for what?
Testing for cancer
Why do some Cystic Fibrosis patients develop intestinal obstruction?
CF patients have a near total absence of electrolyte secretion, causing the intestinal lumen to not be well-lubricated
Name 6-7 substances that act as secretagogues (cause the secretion of another substance) in the intestinal tract
- VIP
- ACh
- Substance P
- Prostaglandins & Leukotrienes
- Histamine
- Serotonin
Name two substances that act to inhibit secretion (or promote absorption) in the intestinal tract.
- NE
- Somatostatin
What cytokine is important for restitution of the intestinal epithelium following an injury / disruption / ulceration?
Name three ways it contributes to the repair process.
TGF-ß
- Fibrogenic
- Inhibits lymphocyte proliferation
- Stimulates surrounding epithelial cells
- Division
- Differentiation
- Migration
What immune cell is especially important for linking the early innate immune response with the late adaptive immune response?
Dendritic cells
On what cell surface of the intestinal epithelium are Toll-Like Receptors (TLRs) found on?
Along the Basolateral Membrane, not the lumenal surface
Where in a host cell are Nod-Like Receptors (NLRs) located?
What does this make NLRs good at detecting?
Within the cytoplasm
Detect intracellular pathogens