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Microimm 2500 > (I) Lecture 2: Innate Immunity Part I > Flashcards

(I) Lecture 2: Innate Immunity Part I Flashcards

1
Q

Pathogens and Innate immunity

A

Most pathogens are effectively stopped by innate immunity at an early stage

Deficiencies in innate defenses are very RARE

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2
Q

Key Properties of Innate Immunity

A
  • very fast (minutes/hours)
  • low specificity (recognizes general molecular patterns)
  • germline encoded (born with it) –> limited diversity (every progeny has the same receptors)
  • no memory (non adaptive = same response w/ each exposure)
  • very good at it. RARELY FAILS
  • innate immunity has the same speed of rxn and same magnitude despite re-exposure WHILE adaptive starts earlier and has higher magnitude w/ re-exposure
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3
Q

The Skin

A
  • epidermis (top layer) and dermis is below

epidermis is made up of
- corneal layer (a keratin “shield”)
- keratinocytes (specialized epithelial cells)

Epithelial cells protect us from the outside world (they line points of entry in digestive and respiratory tracts)

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4
Q

Respiratory Tract

A

lined with cilia and goblet cell

epithelia in respiratory tract is coated w/ mucus (barrier to keep things from coming in and vector for flow of substances

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5
Q

Goblet cells

A

specialized epithelial cells that secrete mucin (main component of mucus) to form the mucous barrier which keep resp. tract moist AND guards from pathogens

keep things away from the cell + keep things moving flushing through system

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6
Q

Cilia

A

sweep microbes and debris up and out of the airways

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7
Q

Lung of a person w/ CF

A

cilia is collapsed w/ thicker, granular mucus that is dried

allows for bacterial infection

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8
Q

Mucocilliary Clearance (MCC)

A
  • CF patients are either missing the CFTR gene or have mutations to the gene = thicker mucus and cilia collapse = NO mucocilliary clearance

perfect for opportunistic pathogens

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9
Q

Gastro-Intestinal Tract

A

Goblet cells and Paneth cells

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10
Q

Paneth cells

A

cells that make antimicrobial peptides (defenses) that inhibit/kill microbes

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11
Q

Epithelial Tissue Types

A

Shapes: cuboidal, squamous, columnar

Simple: single layer
Stratified: multiple layers

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12
Q

Key Properties of Epithelial Cells

A
  • tight junctions btwn cells (prevents pathogens from “squeezing” inside the tissue) – also keeps things from leaking out
  • regeneration (rapidly divide to replace dying cells)
  • desquamation (shedding helps remove attached pathogens)
  • secretions (ex. mucins/mucus MCC, and chemical defenses) – Goblet cells make secretions
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13
Q

Leaky Gut Syndrome

A

Loss of barrier integrity/dysfunction of intestinal epithelial cell tight junctions – allow things to leak out and toxins to come in

Common in inflammatory bowel disease and ulcerative colitis

Increased permeability and triggers inflammation

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14
Q

Gram-positive and gram-negative bacteria

A

Gram-positive bacteria only have a cell membrane and a thick layer of exposed peptidoglycan

Gram-negative bacteria have a double membrane (cell + outer membranes) = encloses thinner layer of peptidoglycan

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15
Q

Chemical Defenses

A
  • secreted by epithelial cells
  • can be microbicidal (kill microbe) or microbiostatic (prevent its growth)
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16
Q

Lysozyme

A

In tears, breastmilk and sweat

Glycosidase that breaks peptidoglycan

More effective against gram-positive bacteria b/c peptidoglycan layer is exposed

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17
Q

Antimicrobial peptides

A
  • chemical defenses
  • produced by immune cells or by epithelial cells
  • short cationic (+ charge) peptides are attracted to neg. charge phospholipid bilayer
  • disrupt cell membrane integrity (bacteria, fungi, viruses)
  • humans make up to 21 diff. defensins
  • ex. defensins, cathelicidins, histatins
18
Q

Microbiota vs microbiome

A

Microbiota: organisms
Microbiome: organisms + genes (specialized for each location)

19
Q

Mechanical barriers

A
  • expel, flush out
  • sneeze, cough, cilia, peristalsis (vomit, diarrhea)
  • secretions: saliva, tears, urine, sweat, ear wzx
  • mucus (goblet cells)
20
Q

Chemical barriers

A
  • fatty acids (skin)
  • enzymes: lysozyme (saliva, sweat, tears), pepsin (gut)
  • low pH (stomach)
  • antimicrobial peptides (not just from epithelial cells)
21
Q

Biological barriers

A
  • microbiota (bacteria, viruses, yeast, etc.)
  • products
22
Q

Microbiome

A

Every surface (potential entry point of pathogen) has a microbiome

  • every microbiota is ADAPTED to its unique environment (different in different parts of the body)
  • vary from person to person (but less than variation in anatomical locations)
  • essential to our health (absence of bacteria = immune defects)
  • shifts RAPIDLY during first months of life (changes based on delivery mode, diet (breastmilk vs formula), solids)
23
Q

Crohn’s disease

A
  • inflammatory bowel disease
  • chronic inflammation of GI tract (indigestion)
  • cause remains unknown

Characteristics
- dysregulated immune system
- altered microbiota
- genetic susceptibility
- environmental factors

24
Q

Gut Microbiome

A

Helps w/ digestion but also keeps pathogens away

  • gut has a lot of commensal bacteria (healthy) and antibiotics kill many of the healthy bacteria
  • C. difficle is a common infection after antibiotics that produces toxins (good bacteria that keep pathogens out are wiped out)
  • After Covid, ppl can have diarrhea after (COV-2 virus can cause microbial imbalance in the body, which allows opportunistic pathogens to colonize the gut)
25
Q

Microbial dysbiosis

A

imbalance of the gut microbiota

26
Q

Opportunistic Pathogens

A
  • pathogens cause disease in healthy indivduals
  • “opportunistic” pathogens cause disease only under SPECIAL CIRCUMSTANCES (ex. immunocompromised, injured, pregnancy)
  • ex. E. Coli, C. diff, Staphylococcus, Listeria)
27
Q

Skin barriers

A

Mechanical
- epithelial cells joined by tight junctions
- longitudinal flow of air/fluid

Chemical
- fatty acids
- beta-defensins

28
Q

Gut barriers

A

Mechanical
- epithelial cells joined by tight junctions
- longitudinal flow of air/fluid

Chemical
- low pH
- enzymes (pepsin)
- alpha defensins

29
Q

Lung barriers

A

Mechanical
- epithelial cells joined by tight junctions
- MCC (mucociliary clearance)

Chemical
- pulmonary surfactant

30
Q

Eyes/nose/oral cavity barriers

A

Mechanical
- epithelial cells joined by tight junctions
- tears
- nasal cilia

Chemical
- enzymes in tears and saliva (lysozyme)

31
Q

Mucus-binding membrane proteins

A

Make pathogens more resistant to being cleared out w/ mechanical forces to get closer to cells

32
Q

UPEC

A

bacteria that adheres to surface of epithelial cells of urinary tract – cause UTI

produce pili that allow them to attach

33
Q

Extracellular phase

A

ALL pathogens have an extracellular phase

sites of infection
- interstitial spaces, blood, lymph, epithelial surfaces

34
Q

Intracellular phase

A

only SOME pathogens have an intracellular phase

sites of infection
- cytoplasmic, vesicular

35
Q

Bacteria

A
  • prokaryotic cells
  • can REPLICATE on their own (binary fission)
  • most bacteria live exclusively EXTRAcellularly
  • some also survive intracellularly (have both extra and intracellular phase)
36
Q

Viruses

A
  • non cellular
  • CANNOT replicate on their own
  • need to infect a host to use their machinery for replication
  • all viruses have BOTH an extra and intracellular phase
37
Q

Types of immune system barriers

A

mechanical, chemical and biological

38
Q

True or False

Innate immunity specificity is germline-encoded

A

True

39
Q

Important features of epithelial cells

A
  • form tight junctions
  • shed to release pathogens
  • secrete antimicrobial peptides
  • secrete mucus
40
Q

The microbiome protects us against pathogens by:

A
  • competing w/ other bacteria for nutrients
  • forming a protective layer over epithelial cells
41
Q

True or False

All bacteria have an intracellular life cycle

A

False

Most only have an extracellular

Microimm 2500 (29 decks)

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