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infection and immunity Flashcards

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1
Q

4 methods of protection against infection

A

physical barrier
chemical barrier
bacteria protection
immunological

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2
Q

physical barrier

A 
tight epi wall 
glycolyx
mucous and unstirred layer 
peristalsis - keep things moving 
epi barrier - Paneth cells - secrete defensins and lysozyme
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3
Q

chemical barrier

A

bacteriacidal enzymes from Paneth cells

acid - stomach

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4
Q

bacterial protection

A

commensal bacteria maintain immune system priming
may attack foreign species
occupy niche

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5
Q

immunological

A

MALT - rich in T and B cells
GALT
BALT - bronchus

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6
Q

GALT

A

adaptive and innate
generate AB
peyer’s patches, caecal patches- lymphoid tissue - in SI
lymphocytes - mesenteria and lymph nodules (where the lymph from villi drain) and isolated lymphoid follicles
disorganised sites of lymphocytes in lamina propria and lymphocytes in interstitial space between basolateral membrane of epithelium - intra-epithelial cells eg T cells and NK cells
NOT GALT - kuppfer cells in liver - phagocytose

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7
Q

what is the GI immune system tolerant against

A

food antigens

commensal bacteria

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8
Q

what is essential for the gut immune system

A

the bacterial microbiota

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9
Q

describe the gut microbiota

A

more bacteria than the cells in our body
4 phyla
many more genes - provide us with the ability to digest

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10
Q

gut microbiota through the GI

A

stomach - pH = few bacteria
colon = exponential increase

number increased with ingested and secreted nutrients
decrease with peristalsis, contractions, defecation

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11
Q

symbiotic bacteria

A

take and provide nutrients and regulation

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12
Q

commensal bacteria

A

occupy a niche

prevent adhesion of pathogens

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13
Q

pathogens

A

cause inflammation

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14
Q

describe dysbiosis

A

regulation interrupted and inflammation occurs

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15
Q

causes of dysbiosis

A 
infection 
diet 
xenobiotics 
hygiene 
genetics
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16
Q

diseases caused by dysbiosis

A

brain - stress, autism, MS
lung - asthma
liver - NAFLD, NASH
adipoise tissue - obesity, metabolic disease
intestine - IBD, coeliac
systemic disease - T1DM, atherosclerosis, rheumatoid arthritis

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17
Q

MALT

A

submucosa below epithelium
contain lymphoid follicles
follicles surrounded by HEV postcapillary venules = easy passage of lymphocytes
eg oral cavity

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18
Q

peyer’s patches

A

aggregated lymphoid follicles
covered by follicle associated epithelium
this has no goblet cells, secretory IgA or microvilli
have M cells
in SI - most in distal ileum
immune sensors - monitor local bacteria, protect against pathogenic bacteria
development needs exposure to bacterial flora
hit maximum 250 by teenage years
rich in B cells, T cells, macrophages and dendritic cells

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19
Q

M cells

A

the way that antigen uptake occurs in FAE
have IgA receptor
facilitate transfer IgA bacteria complex into Peyer’s patches
antigens presented to lymphocytes = activation

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20
Q

describe trans-epithelial dendritic trees

Study These Flashcards
A

DC
perform antigen sampling
thin extension - bring back into organ
DC form TJ with epi - doesn’t allow entry of pathogens

21
Q

describe the actiation of B cells

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A

mature naïve B cells express IgM
when antigen presented to B cell - class switch to IgA
T cell and B cell influence maturation by cytokines
B cell mature to become mature IgA secreting plasma cells
populate the lamina propria

22
Q

describe thymus dependant B cell maturation

Study These Flashcards
A

B cell meets antigen
if correct antigen - T cell gives B CD40L
B cell is activated

23
Q

describe the formation of secretory IgA

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A

in submucoisa - dimeric IgA binds to poly-Ig receptor on basolateral membrane
taken into vesical
enzymatic cleavage
makes secretory IgA

24
Q

action of sIgA

Study These Flashcards
A

neutralisation

25
action of secretory component
protects against the gut
26
mucus in LI
there is a lot | doesn't let bacteria in
27
describe lymphocyte homing
lymphocyte in circulation and secondary lymphoid tissue if find correct antigen - most likely to go back to organ it found the antigen - thinsk more likely to meet more antigens
28
describe extravasation of lymphocytes
rolling fascilitated by weak binding of selectin strong α4β7 integrin (on lymphocyte)/MAdCAM-1 (on epi) binding causes activation and arrest of lymphocyte - homing back to gut
29
mechanism of cholera infection
acute bacterial disease - vibro cholerae serogroups O1 and O139 - cholera toxin gram -ve comma shaped bacteria reach SI make close contact with epi - releases toxin cause exit of Na K Cl and water = diarrhoea
30
transmission of cholera
faecal oral - contaminated water and food
31
symptoms of cholera
severe dehydration and diarrhoea vomiting nausea abdominal pain
32
diagnosis of cholera
bacteria culture from stool sample on selective agar | rapid dipstick tests are also available
33
treatment of cholera
oral rehydration | vaccine - for travellers - Dukoral, oral, inactivated
34
viral infections causing diarrhoea
rotavirus | norovirus
35
bacterial causes of diarrhoea
``` campylobacter jejuni E coli salmonella shigella C difficiile ```
36
protozoal parasitic
giardia lambia | entamoeba histolytica
37
describe rotavirus
RNA replicates in enterocytes types A - E A most common - human infections most common cause diarrhoea in infants and young children ] treatment - oral rehydration therapy vaccination - live attenuated oral vaccine - rotarix against Type A
38
describe norovirus
``` RNA diagnosis - PCR symptoms - acute gastroenteritis recovery - 1-3 days transmission - faecal-oral route - up to 2wks outbreaks occur in closed communities ```
39
descrive campylobacter
transmission - undercooked meat, untreated water, unpasteurised milk - low infective dose treatment - not necessary, azithromycin, fluroquinolones - resistance so means problematic
40
describe enterotoxigenic E coli
cholera like toxin | watery diarrhoea
41
describe entrovasive E coli
shigella like illness | bloody diarrhoea
42
describe enterohaemorrhagic or shiga toxin producing E coli
loss of kidney function
43
describe C difficile
normally in epi - do no harm on AB microbiota killed C difficile = pathogenic destroy lining = leakage of neutroohil and RBC = bloody diarrhoea treatment - stop current AB treat with metronidazole, vancomycin high recurrence - increasingly difficult to treat can treat with faecal microbiota transplantation
44
describe coeliac disease
gliadin not broken down in stomach - reach SI - bidn to sIgA - transferred to lamina propria innate immune detection -T cell developmet - T and B co-stim - cytokines, chemokines and their receptors symptoms - abdominal distension, diarrhoea diagnosis - Ab blood tests- anti-gliadin, biopsy of duodenum treatment - gluten free diet
45
describe IBS
visceral hypersensitivity - triggered by diet and stress symptoms - recurrent ab pain, abdominal bowel motility, constipation/diarrhoea treatment - diet modiufication (avoid apples, beans cauliflowers, constipation - soluble fibre, stool softeneers, osmotic laxitives, spasms and pain - anti-diarrheals, anti-muscarinic management of stress, anxiety and depression
46
describe crohn's disease
distal ileum and colon patches of inflammatory damage - cobblestone appearance symptoms - diarrhoea, ab cramp, fever, anaemia, weight loss and fatigue diagnosis - Ab blood tests, endoscopy and barium x-ray treatment - anti-inf drugs, immunosuppressants, surgery - not curative
47
describe ulcerative colitis
colon only continuous inflammation bloody diarrhoea, ab cramp, anaemia, weight loss, fatigue diagnosis - Ab blood tests, endoscopy and barium x-ray treatment - treatment - anti-inf drugs, immunosuppressants, colorectomy - curative
48
mechanism of IBD (irritable bowel disease) ie Crohn's and ulcerative colitis
``` 2/3 genes identical lining destroyed bacteria entry stimulate immune celk regulation falls constant action chronic infection colon cancer ```

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