Med Micro 3 - 1st Line (mucous etc) Flashcards
Mucous membranes
Line all body cavities open to the outside. 2 layers: epithelium and connective layer (deeper). Goblet cells secrete mucous.
Lacteal and function
A capillary of the lymph system. During an infection, blood vessels get leaky and empty into lacteals. Leads to lymph node unidirectionally
Lymph node
Lacteals empty in there. Important in adaptive immunity.
Epithelium of mucous membrane
Thin outer layer covering mucous membrane. Living cells. Packed tightly (no crossing for pathogens). Constant shedding and movement (peristalsis). Secrete defensins
Defensins - what are they? Where are they found?
Anti-microbial peptides. Found on skin (in sweat), in mucous and neutrophils. Amphipathic.
How are defensins triggered? What is their function?
Punch holes in bacterial membrane and cause leakiness; enter cell and disrupt pathways; or promote chemotaxis. Triggered by sugar and PAMPs
Compare skin and mucous membranes
Chart
Lacrimal apparatus
Makes and drains tears (into nasal cavity, then throat). Contain lysozyme, lactoferrin (binds free iron) and salt.
PAMPs and examples
pathogen-associated molecular patterns. ex. LPS and peptidoglycan, lipoteichoic acid, nucleic acids. We have receptors for them on our phagocytes
Interest in defensins
Could be used as an antibiotic, and they enhance killing by antibiotics (more can access the cell)
What kind of structure may protect a pathogen against defensins?
Capsules, S-layers outside cell, proteases
How do you activate a phagocyte?
Cytokines from keratinocytes, PAMPs
Pattern recognition receptors
in innate immune cells, identify PAMPs, Some external and some internal ex. TLR and NOD
Toll-like receptors (TLRs)
At least 13 types which recognize specific molecules (PAMPs). Identify live and dead bacteria or metabolites. Critical in innate immunity.
What types of cells are most likely going to express TLRs?
Dendritic cells, phagocytes
Action of TLRs
Binding can result in cytokine production, defensin secretion, phagocytosis and antigen presentation, interferon production, apoptosis
Based on some of the virulence factors we’ve discussed so far, what types may help a pathogen avoid TLRs?
Signals for internalization of internal pathogens, clotting (cloaking), etc
Nucleotide Oligomerization Domain (NOD) Proteins
Intracellular receptors for PAMPs. In adaptive immune response (MHC II presentation). Mediate inflammation (chemokine production), apoptosis, and possibly defensins
Mutation in NOD
Mutation in NOD2 can cause Crohn’s disease (auto-immune disease).
Chemokines
Involved in chemotaxis. Released by cell to recruit help (important in momement).
MHCI and II
MHCI are antigen presenting cells resulting from viral infections. MHCII present epitopes after phgocytosis.
Epitope
A small part of the antigen
Antigen types
Exogenous, endogenous, auto-antigens. NOT always something foreign.
How does microbial antagonism regulate the growth of other bacteria?
Based on normal microflora. Finite nutrients (like Fe), defensins (microbes make them too), reduce binding sites, help activate innate immune response, create unfavourable environment (pH)
Some of our body’s defenses are used (subverted) by pathogens to provide an avenue for entry. Give examples.
Infect phagocytes which signal chemokines to helper T cells and infects them (HIV); get through lacrimal apparatus to get into the throat (cold); use phagocytosis to get in then escape phagosome.
