Host-defense system

Question 1

occludin

Answer 1

tight junction protein

Question 2

goblet cell

Answer 2

releases mucus

Question 3

first line of defense

Answer 3

skin and mucosa

Question 4

steps to bacterial infection

Answer 4

attachment, invasion of host tissues, colonizes the tissue, colonization/replication that causes damage to host cells, exit, spread to other cells

Question 5

epithelium

Answer 5

-differs between tissues because the function varies

Question 6

tight junctions and desmosomes

Answer 6

protein structures that tightly bind the epithelial cells together

Question 7

endothelium

Answer 7

• example: blood vessels
• these cells are not as tightly held together so cells of the immune system can move across them.
• Bacteria take advantage of this and can also move across.

Question 8

basolateral surface

Answer 8

surface of the cells that is attached to the basal lamina

Question 9

basal lamina

Answer 9

thin sheet of connective tissue that the epithelial cells are connected to

Question 10

apical surface

Answer 10

the surface of the cells that is facing outward

-basolateral and apical surfaces are polarized ie they have different protein compositions

Question 11

what are the defenses of the skin? (6)

Answer 11

• dry, acidic environment with lower temperature (35C)
• dead keratinized cells
• sloughing of surface cells
• toxic lipids and lysozyme
• normal microbiota
• uderlying immune cells (SALT)

Question 12

SALT

Answer 12

skin-associated lymphoid tissue (Dendritic cells, Langerhans)

Question 13

what are the defenses of mucosal layers? (5)

Answer 13

• mucosal cells are regularly released into the lumen and replaced
• It is one of the fastest dividing cell in the body, so the bacteria would need to divide faster than it was ejecting it in order to colonize.
• mucus contains lysozyme
• antibodies
• cryptdins and defensins are antibacterial peptides produced by the host that are toxic to many bacteria

Question 14

MALT

Answer 14

mucosa-associated lymphoid tissue

Question 15

GALT

Answer 15

gut-associated lymphoid tissue

Question 16

How do bacteria resist lysozyme?

Answer 16

• protease
• capsule
• gram negative

Question 17

Antimicrobial peptides

Answer 17

• 20-30aa
• positive and hydrophobic region
• eukaryotic cells have a neutral charge. Bacterial cells have a negative charge due to LPS in gram neg and TA/LTA in gram pos

Question 18

How do bacteria resist antimicrobial peptides?

Answer 18

• adding a positive aa to the negative to make it neutral
• capsule
• production of peptidase

Question 19

normal microbiota

Answer 19

commensals colonize the host without causing damage

• can provide metabolic rxns for the host ie synthesize vitamins
• play a teaching role in the immune system of host
• Some resident bacteria produce bactericidal compounds such as pore-forming toxins (bacteriocidins) and growth inhibitors (remember that bacterial species are competing against each other
• It competes with incoming pathogens for essential nutrients (iron)
• occupies surfaces, so pathogens cannot colonize them

Question 20

defenses of specific sites

Answer 20

eyes
stomach
airway
small intestine
colon
vaginal tract
bladder