Survival & Body Defence

Question 1

Give 4 physical requirements for microorganism survival

Answer 1

Moisture
pH
Temperature
O2

Question 2

Explain 3 other survival requirement factors for microorganisms

Answer 2

Chemical toxicity: bile salts, skin fatty acids, lysozymes
Available nutrients: low free Fe supply in body fluids
Competition: growth inhibiting bacteriocins (proteins)

Question 3

Describe the ocular defence

Answer 3

Protective orbit (lids, lashes, brows)
Active tear flow (dilutes toxic stimuli)
Corneal epithelium (tight junctions, microvilli)

Question 4

Describe the tear film layers and it’s purpose

Answer 4

Corneal nutrition/O2 supply/lubrication/removes foreign materials/waste ~

Lipid: smooth surface slows aq layer evaporation
AQ: lac gland, APPs, metabolites, electrolytes
Mucus: GCs/MUC 1, 4, 16 ~ trap, coat, remove debris

Question 5

How do antimicrobial peptide tear proteins function?

Answer 5

Lysozymes digest gram+ bacteria cell wall
Lactoferrin binds to high aff. Fe
Lipocalin stabilises lipid layer
Mucins form gel to trap, coat, remove
Cytokines ~ signal molecules
IgA - infection protection for surface

Question 6

Explain immune privilege for the eye

Answer 6

Apoptosis, no lymph system, no ocular supply

Blood retinal barrier (iris, ciliary body, retina ~ less likely inf. response to antigen

Question 7

Explain hypersensitivity and allergens

Answer 7

Excessive immune response/reaction

Asthma, Rhinitis, Conjuctivitis, eczema, GI disorders

Genetic/environmental factors for allergy absorption

Question 8

Describe the innate (non-specific) and acquired (specific) defence mechanisms and their features

Answer 8

Innate: no resistance, host response similar 2nd time (phagocytes/natural killer cells mediated by defensins interferons)

Acquired: resistance develops (memory) ~ T/B lymphocytes, APCs, Mast cells mediated by antibodies

Both mediated by cytokines/compliment proteins