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cellular basis of immunity > 7 - fungi and parasites > Flashcards

7 - fungi and parasites Flashcards

1
Q

why are chronic infections common caused by fungi and parasites

A

they have many adaptions

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2
Q

features of fungi

A

can be uni or mulitcellular
often commensal
contribute to nutrient recycling
can be dispersed by airborne spores

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3
Q

unicellular fungi

A

yeasts

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4
Q

multicellular fungi

A

filamentous

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5
Q

endemic mycoses

A

groups of fungi that occupy ecological niches

geographically located due to climate
often thermally dimorphic

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6
Q

example of commensal fungi

A

microbial flora

e.g.candida albicans

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7
Q

example of fungi dispersed by airborne spores

A

aspergillus fumigatus

reaches terminal air spaces of lungs

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8
Q

types of mycoses

A

endemic mycoses
environmental saprophytes
human commensal fungi

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9
Q

examples of endemic mycoses

A

histoplasma
coccidiodes
blastomyces
paracoccidiodes

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10
Q

where are histoplasma found

A

often mississipi/ohio

bird/bat poo (guano) in soil

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11
Q

where are coccidiodes found

A

arid desert areas (south west USA)

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12
Q

where are blastomyces found

A

near lakes/river valleys

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13
Q

where are paracoccidiodes found

A

tropical and sub forests in South america

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14
Q

examples of environmental saprophytes

A 
aspergillus
rhizopus
absidia
mucor
cryptococcus
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15
Q

features of environmental saprophytes

A

often opportunistic and invasive

dangerous

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16
Q

where is aspergillus often found

A

decaying veg matter

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17
Q

where is cryptococcus found

A

soil with pigeon poo (guano) and eucalyptus trees

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18
Q

examples of human commensal fungi

A

candida albicans

dermatophytes

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19
Q

where is candida albicans often found

A

bowel

pharyngeal flora

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20
Q

where are dermatophytes found

A

keratinized tissue

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21
Q

fungi mortality rate?

A

high in infected populations

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22
Q

example of high mortality rate of fungi

A

Aspergillus fumigatus causes more than 200,000 life threatening infections per year

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23
Q

persistant superficial infection of candida albicans

A

causes disription of mucosal barriers

e..g thrush

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24
Q

candida albicans in immunocompromised

A

disseminates to life-threatening diseases

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25
prevalence of candida albicans
most common human infection 4th most common nosocomial bloodstream infection in USA --> very expensive for government
26
candida albicans virulence
``` reproduces asexually (budding) dimorphic in repsonse to microenvironmental signals ```
27
dimorphic
transition from yeast to filamentous
28
role of yeast form candida albicans in infection
disseminates easily in bloodstream
29
role of filamentous c. albicans in infection
facilitates invasion and evasion of phagocytosis
30
if c albicans has no dimporphic switch
it is non pathogenic
31
innate host recognition of fungi
interactions with cell wall components | PAMPs
32
examples of fungi PAMPs
glucans mannans galactans
33
dectin-1
c-type lectin highly conserved on surface of dendritic cells important in anti-fungal immunity
34
role of c-type lectin carbphydrate recognition domain
mediates recognition of B1,3-glucans and B1,6-glucans and zymosan
35
dectin-1 interacts with ITAM in cytoplams
tyrosine phosphorylation | then acts together with TLRs to induce inflammatory cytokines and ROS
36
ITAM
immunoreceptor Tyrosine-based Activation Motif important in signal transduction found in T cells, B cells and Fc domains
37
4 examples of PRR that recognise fungi/parasites/viruses
Dectin-1 Dectin-2 Mincle CLEC5a
38
knock out dectin-1 genes in mice infect with candida albicans what happens
mice susceptible and die | evidence that dectin-1 is important in anti-fungal immunity
39
importance of TLRs
distinguish between pathogenic molecules and normal apoptotic particles
40
what to TLRs stimulate
cytokine production and secretion --> inflammatory response | initiation of adaptive immune response
41
what do most TLRs signal through
MyD88
42
what is MyD88
myeloid differentiation factor 88 adaptor protein
43
role of MyD88
binds to TLR after activation by fungal component (PAMP) and CD14 initiates signalling cascade
44
Syk
enzyme (spleen tyrosine kinase) important in signal transduction
45
MBL
mannose-binding lectin
46
mannose binding lectin
collectin protein opsonin coupled to complement pathway via MASPS bind to MASPS to cause conformational chage
47
oxidative burst killing mech
kill by rapidly producing and releasing ROS
48
what is chromoblastomycosis
a chronic but non-fatal fungal infection of the skin and subcutaneous tissue usually caused by F. Pedrosi
49
helminth
class of parasite that can cause disease in humans
50
why do helminths require an intermediate host
they do not replicate within the host
51
examples of helminth intermediate host
soil | water
52
3 larval stags of sexual reproduction of helminths
nematodes trematodes cestodes
53
what is schistosoma
the most important trematode (fluke) infection of humans
54
vector of schistosoma
water snail
55
vector of schistosoma
water snails become infected by eggs in fresh water miracidia mature and multiply to release more cercariae
56
which stage is dangerous for causing infection of schistosoma
motile | fork-tailed cercariae
57
what happens when free swimming cercariae come in contact with host skin
use proteases and muscular action of oral sucker to penetrate host skin head enters body shed tails
58
what do cercariae transition into
schistosoma and then into a schistosome
59
where do immature schistosomula migrate to
the liver microcirculation to mature
60
male/female interaction of schistosomula
females reside in a canal within the male pairs then migrate against the venous flow from the GI tract to the liver eggs are released into the veins
61
impact of schistosome eggs being released into liver veins
elicit granulomatous inflammatory response
62
T helper cell response to schistosome eggs
early stage - Th1 profile directed at schistosomula | Th2 response then takes over against egg antigens
63
granulomatous response to schistosome eggs
granulomas surround eggs recruit eosinophils, IgE, Th2 characteristics of schistomiasis shown granulomas then translocated to the intestinal lumen and then excreted
64
what happens when granulomas dissipate
collagenous scars coalesce and cirrhosis develops | blood bypass channels (varices) form and bleed to cause death
65
what are protozoa
``` class of parasite unicellular ```
66
why are protozoa good at chronic infections
they have lots of evolutionary adaptations
67
why is antigenic variation important
underlies capacity of organisms to survive in a host
68
how are the two groups of protozoal infections introduced
1. by bites or tissue injury | 2. by ingestion of contaminated water
69
trypanosoma cruzi
protozoa that causes mega colon | kissing beetles penetrate skin and take blood meal to infect body
70
what causes african sleeping sickeness
protozoa parasite | trypansoma brusei
71
VATs
variable antigen type
72
how does antigenic variation allow escape from host defences
successive dominance of each series of a variable antigen type (VAT) over time
73
VATs cause appearance of remission in trypansosomes
antibodies destroy homologous trypanosomes almost successful clearance parasites then express new VSG thus becoming a new VAT and multiply
74
VSG
variant-specific surface glycoprotein
75
VSG release
VSG is released through flagellar resevoir and covers parasite as a surface coat
76
where are VSG expression sites
at the ends of chromosomes
77
role of syk
adaptor protein for dectin-1 (PRR) | enhances signalling

cellular basis of immunity (21 decks)

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