Module 2.0: Host Defence System

Question 1

What are the steps involved n bacterial infection

Answer 1

1. Bacteria attaches to the host
2. Bacteria invades the tissue
   
   1. can be mediated by other orgranisms, like fleas
3. Bacteria colonized the tissue
4. Colonization/replication causes damage to the tissue
5. Bacteria exit the host to infect others
   
   1. flea taking blood meal from infected host onto new host
6. Transmission to a new host

Question 2

Why does bacteria colonise tissue

Answer 2

1. To establish infection
2. Create proper conditions for replications
3. hide or fight from host immune system

Question 3

Name the Defenses of the host agasint bacterial pathogens with examples

Answer 3

1. First line
   
   1. skin
   2. mucosa
2. Innate immune system ⇒ PANNIC
   
   1. inflammation
   2. complement
   3. phagocytes
   4. NK cells
   5. neutrophil extracellular traps
   6. apoptosis
3. The adaptive immune system CAAM
   
   1. antibodies
   2. CTLs
   3. Activation of macrophages
   4. Memory

Question 4

Give more in-depth examples of skin and mucosa, ask for my discriiptive something from someone else

Answer 4

1. Simple squamous epithelium
   
   1. mouth and lungs
2. Startified squamous epithelium
   
   1. skin + vaginal track
3. Cilated columnar epithelium
   
   1. upper resp tract
4. Simple cubodical epithlium
   
   1. kidey
5. Simple colummnar epithim
   
   1. intestinal track
6. Connective tissue
   
   1. below bsala lamina, there are other cells in the matrix

Question 5

ASK aboutmslide 7

Answer 5

• pathogens do not like barrier
• many intsential pathogens through water and food which are able to destrod tide junctions
• Occludin: tide junction protein that keeps it close
• when u attach e coli to occuldin, there will be less occulin
• meaning e coli disrupts that protein, making it less present
  
  • increase permability
  • disease can go through
• mutants dont have type 2 secretion systems, unable to destroy occludin

Question 6

What does the skin epithelium consit of, how are they structured

Answer 6

• consist of layers of cells that covers all surface of the body expose to the external environment.
• epithelium of tissues differ because they fulfill different functions
• cells are attached to htin sheet of connective tissue called basal lamina which is made of an extracellular matrix component

Question 7

What is the bsolateral surface//What is apical surface

Answer 7

• surface of the cells attached to basal lamina

-surface of cells facing outwards, may have varying protein compositions meaning the cells are polarised like intestinal mucosa

Question 8

Compare cells in epithelium vs endothelium

Answer 8

• Epi: tightly bound together by protein structures, eg: mucosal epithelium is bound in tight junction and desmosome structures
• Endo: not tightly bound so immune system cells can move freely across surfaces meaning bacteria can easily cross

Question 9

Desrcibe and draw skin structure

Answer 9

• dead cells make thick layer of protein
  
  • Sloughing of dead cells
    
    • dead cells often gets stripped away, by doing that we remove bacteria that has colonised ur skin
    • bacteria that wants to colonise must grow faster than we shed
• SALT are cells (DC + macrophage) there to patrol, sensors waiting for molecules of pathogens
• sweat glands/ hair follicules can be entrance point for pathogens

Question 10

What is SALT

Answer 10

• skin-associated lymphoid tissue
• DC + macrophage
• Langerhans

Question 11

What are defenses of mucosal surfaces

Answer 11

• regulary replaced and old cells ejected to the lumen
• one of the fastest diving cells, bacteria that manage to attach then must grow fast enough to colonise newly produced cells

Question 12

MALT/GALT

Answer 12

What are MALT

• Muscosa associate lympod tissue (DCs, T cells, macrophages

What is GALT

• gut associated lympoid tissue (made of like MALT)

Question 13

Name sites and specific defense

Answer 13

• eyes: tears, washes away and antibacterial substances
• airway entrance: mucus traps, ciliated epithial cells propel bacteria laden mucus away
• stomach: acidic encuroment
• small intensine: rapid dlow of ocntents,sloughing of epithieal cells
• colon: resistant microbiota, sloughling of epithial cells, flow of content
• vafginal: resident microbiota, slooughing…, flow of vaginal fluid
• bladder: spincheter kepps bacteria out, flushing of urine washes bactiera out of bladderr