Immunity and Infection Flashcards
(222 cards)
1
Q
What is the innate immune response?
A
Non specific defence mechanism
Host uses immediately/within several hours after exposure to antigen
2
Q
What are 4 characteristics of the innate immune response?
A
Born with it
V fast
Responds same way each time
Induces + directs acquired/adaptive immune response
3
Q
What enzyme is in tears, sweat and saliva that protects body and what does it do?
A
Lysopzyme
Destroys bact walls
4
Q
What antibacterial compound does the skin produce and what bact is it active against?
A
Psoriasin
E coli
5
Q
What is primary cilia dyskinesia?
A
Can’t make cilia/ cilia x move
Recurrent lung infections
6
Q
What is PAMP?
A
Pathogen Associated Molecular Patterns
7
Q
What 2 features must PAMP have?
A
Present in microorganism, x host
Essential to survival of pathogen
8
Q
What is the PAMP in:
a) Gram negative bacteria?
b) Gram positive bacteria?
A
a) Lipopolysaccharide (LPS) in cell wall
b) Lipoteichoic acid in cell wall
9
Q
What is PRR?
A
Pattern Recognition Receptor
10
Q
What are the 3 types of PRR?
A
Collectins
Toll-like receptors
Nod-like receptors
11
Q
What are 2 regions of collectins?
A
Collagen like region - interacts effector prts immune system
Lectin region - binds sugar molecules on surface of pathogen e.g. mannose
12
Q
What do these toll-like receptors recognise?
a) TLR 3
b) TLR 5
c) TLR 9
A
a) Double stranded RNA
b) Flagellin in bact
c) Unmethylated CpG DNA in bact
13
Q
What does NOD stand for?
A
Nucleotide Oligomerization Domain
14
Q
Where are complements synthesised and when?
A
Liver
In response to inflammation
15
Q
What is the key complement protein and what enzyme activates it?
A
C3
C3 convertase
16
Q
What are 3 ways complements are activated?
A
Classical
Alternative
MB-lectin
17
Q
How are the 3 complement activating pathways triggered?
A
Classical - antigen-antibody complex
MB-lectin - mannose residue on pathogen
Alternative - pathogen spontaneously activates
18
Q
What molecules are formed from the cleavage of C3?
A
C3a - smaller
C3b - larger
19
Q
What does C3a do?
A
Diffuse away from site of infection
Binds C3a receptor in macrophage + neutrophils
Recruits them to site of infection
20
Q
What does C3b do?
A
Coats pathogen - opsonization
21
Q
What is the MAC and what does it do?
A
Membrane Attack Complex
Makes pore that inserts ==> bact cell wall, destroy by lysis
22
Q
What protein is MAC activated by?
A
C3
23
Q
What is the difference between macrophage and monocyte?
A
Monocyte - In bloodstream
Macrophage - In tissue
24
Q
Name 3 features of monocytes/macrophages
A
Mature from circulating monocyte
Large no in GI tract, lung, liver, spleen
Relativ long lived
25
Name 2 features of neutrophils?
Only in blood
| Short lived
26
What reactive intermediates are in neutrophils and what are they involved in?
O2 intermediates
| Respiratory burst
27
What enzyme reduces O2 to make O2 radicals?
NADPH oxidase
| Form hydroxyl radicals + hypochlorite
28
What is the effect of reactive O2 and N2 intermediates on bacteria?
DNA damage + alterations to bacterial membranes
29
Why are O2 radicals regulated and how?
X specific to bacterial cells so can damage host cells
| Rapid conversion to harmless products
30
What reactive intermediates are in macrophages?
N2 intermediates
31
Equation for formation of NO radicals + enzyme?
O2 + L-arginine ==> L-citrulline + NO radicals
| NO synthase
32
What are the most potent activators of NO synthase?
Interferon gamma
| Tumour necrosis factor
33
What molecules do cytokines activate in the innate immune response?
```
IL-1 (interleukin 1)
IL- 6 (interleukin 6)
TNF alpha (turnover necrosis factor alpha)
```
34
What is the role of chemokines?
Promote inflammation by enabling cells to adhere to surface of blood vessels + migrate to infected tissue
35
What are the 2 type 1 interferons and when are they produced?
IFN alpha
IFN beta
Produced in response to virally infected cells
36
What does pleiotropic mean in context of chemokines?
When 1 chemokine receptor can bind >1 chemokine
37
Name 3 features of natural killer cells?
Kill virally infected cells + tumour cells
Response to TNF alpha, IL-12
Produce IFN gamma
38
Name 2 functions of critical cytokines
Activate macrophages
| Upregulate MHC molecules
39
What do critical cytokines do with IL-12?
Stimulate differentiation of CD4 Th1 cells
40
What are the antigen presenting cells in body?
Macrophages
B cells
Mature dendritic cells activate T cells
41
What is the T cell receptor made up of and how many antigen binding sites does it have?
Alpha and beta chain - heterodimer
| 1
42
What is the B cell receptor made up of and how many antigen binding sites does it have?
2 identical heavy chains
2 identical light chains
2
43
How quicky does the innate immune response act?
Within 96 hours
44
How quickly does the adaptive immunity response act?
```
1st exposure (Primary response): 12 days
2nd exposure (Secondary response): 5-7 days
```
45
What 3 regions make up the antibody heavy chains and how many different options for each?
Total diff combos for heavy region?
Variable - 48
Diversity - 27
Joining - 6
48 x 27 x 6 = 7776
46
What 2 regions make up the antibody light chains?
| Total diff combos for light region?
Variable
Joining
340 variants
47
What is the total no of variants for antibody (heavy + light chain combined)?
Name?
7776 x 340 = 2, 643, 840 variants
| Combinatorial diversity
48
What is junctional diversity?
Joining of diff regions in antibody chains x precise
| Nucleotides added + removed during rearrangement
49
Where are
a) B cells
b) T cells
developed with gene rearrangement?
a) Bone marrow
| b) Thymus
50
What is another name for antibodies?
Immunoglobins
51
What are the 2 types of light chains in antibodies?
Kappa/Lamda
52
What are Fc receptors?
Paired constant region segments
53
What are 4 functions of antibodies?
Neutralise toxins + viruses
Opsonise pathogens
Activate complement cascade
Agglutinates particles
54
What are 3 features IgG?
Good at opsonization
Antibody-dependant Cellular Cytotoxicity
4 subclasses of IgG
55
How is a IgA dimer formed?
2 monomers joined by J chain
56
How do you measure specific IgG?
Measurement of antibody titre in serum in response to a vaccine
57
How many binding sites does a IgA dimer have and what can they do?
4
Agglutination + neutralisation
Retention of antigen by adherence to mucus
58
What is the 1st antibody made in the immune response?
Pentameric IgM
59
How many binding sites does pentameric IgM have and what is this called?
10 binding sites
| High avidity
60
What cells have receptors for IgE?
Mast cells
61
What type of antibodies do people with allergies have a higher concentration of?
IgE in serum
62
What cells can improve their specificity for antigens?
Only B cells
63
Where are germinal centres found?
Secondary lymphoid tissues contain zones of dividing B cells
64
What is affinity maturation of B cells?
B cells mutate immunoglobulin variable region genes by somatic hypermutation
High affinity variants are selected
65
What 2 types of cells leave the germinal centre?
Memory cells
| Plasma cells
66
What are the 2 locations plasma cells migrate 2 and what antibodies do they produce?
Intestines ==> IgA
| Bone marrow ==> IgG
67
What is 1 feature of bone marrow plasma cells?
V long lived
| Secrete protective antibodies for lifetime
68
What is a chimeric MA?
Mouse MA engineered so variable region of heavy region of heavy + light chains associated mit human contact regions
69
What is the ending for chimeric MA?
-ximab
70
What is an example of a chimeric MA?
| Function?
Rituximab
Antibody to CD20 receptor, present in B cells
Targets B cells for killing, remove from circulation + lymphoid tissue
Effective against B cell lymphoma + rheumatoid arthiritis
71
What is a humanised MA and what is the ending?
Prts of variable region that contact antigen are from mouse
| -zumab
72
What is an example of a humanised MA?
| Function?
Omalizumab
Specific to IgE
Treat moderate-severe asthma
73
What is the ending of fully human MA?
-umab
74
What is an example of a human MA?
| Function?
Adalimumab
Specific to TNF alpha
Treat inflammatory diseases
75
What is plasmapheresis?
Plasma separated from blood cell
Replaced mit another solution e.g. saline/albumin
/ treated + returned to body
76
What bonds holds together the light and heavy chains in antibodies?
Disulfide bonds
77
What is the name of the antigen encoded by MHC genes?
Human Leukocyte Antigens (HLA)
78
What does MHC stand for?
Major Histocompatibility Complex
79
Name 3 features of MHC I
Single chain
Associate non-covalently to beta-2 microglobulin
Endogenously expressed on all nucleated cells
80
Name 2 features of MHC II
Alpha-beta heterodimer
| Expressed on specialised antigen presenting cells
81
What type of proteins do
a) MHC I molecules
b) MHC II molecules
present?
a) Endogenous proteins
| b) Exogenous proteins
82
Name 5 features of T Cell receptors (TCR)
```
Heterodimer
2 chains joined by disulphide bridges
2 subtypes alpha-beta, gamma-delta
Consists of variable + constant domains
TCR genes undergo rearrangements from germline before translation
```
83
What type of T cells interact with MHC I molecules?
CD8+ (Cytotoxic T cells)
84
What type of T cells interact with MHC II molecules?
CD4+ (Helper T cells)
85
What occurs in signal 1 during T cell response?
TCR (T cell receptor) encounter antigen presenting cell bearing MHC receptor
86
What occurs in signal 2 during T cell response?
Co-stimulation
| CD28 receptor on T cell binds to CD80/86 on antigen presenting cell (APC)
87
What are the 4 diff types of cells CD4+ cells can differentiate into and in response to what?
Th1 - Viruses + intracellular pathogens
Th2 - Extracellular parasites
Th17 - Extracellular parasites + fungi
Treg- Modulate immune response (Regulatory T cell)
88
How do Th1 T cells help immune response?
IL-2 helps CD8+ T cells to proliferate
| IFN-gamma helps macrophages
89
How do Th2 T cells help immune response?
Promote division, affinity maturation of B cells
| Promote eosinophils
90
How do Th17 T cells help immune response?
Epithelium + fibroblast surfaces - secretion of antimicrobial peptides
Promoting maturation of neutrophils - attract to infection site
91
What are 5 functions of Treg cells?
```
Suppress:
Stimulatory activity of APC
Proliferation of responder cells
Cytokine production of responder cells
Antibody production from B cells
Functions of NK + NKT cell
```
92
What are the precursor cells from the bone marrow that enter the thymus?
Thymocytes
93
Where does positive selection for self MHC occur?
Thymic cortex
94
Where does negative selection for T cells occur and what cells?
Thymic medulla
| Thymic Medullary Epithelial Cells (TMECs)
95
What type of antigens do TMECs present?
Tissue Restricted Antigens (TRAs)
96
What are 5 peripheral proteins TMECs express and what peripheral tissue are they usually found?
```
Serum amyloid P - Liver
Trypsin - Pancreas
Insulin - Islets of Langerhans
Crystallin - Eye (Lens)
Thyroglobulin - Thyroid
```
97
What is Autoimmune Polyglandular Syndrome (APS 1)?
Failure of TMECs express TRAs
98
What are 2 peripheral mechanisms of immune intolerance?
Anergy
| Regulatory T cells
99
What is anergy?
Absence of normal immune response to partic antigen/allergen
100
What is anergy important for?
Tolerance to:
Antigens x expressed in thymus
Food antigens
Commensal bacteria (living in body)
101
How do Treg cells affect Th cells?
X proliferation
X/alter cytokine production
Reduce co-stimulation
102
What are the 2 main types of Treg cells?
nTreg
| aTreg
103
Where are:
a) nTreg
b) aTreg
produced?
a) Thymus
| b) Developed from naive T cells in periphery
104
What do nTreg do?
Respond to self antigens
| Protection autoimmunity
105
What do aTreg do?
Constant low level exposure to antigen
Protection autoimmunity
Regulation of responses to food antigens
106
What are PAMPs?
Pathogen Associated Molecular Proteins
| Conserved products of microbial metabolism
107
What are 3 features of PAMPs?
Unique to microbes
Invariant between members of a given class
Vital for microbial fitness
108
How do lymph nodes get swollen?
Dendritic cells migrate to nodes + secrete cytokines + chemokines
Upregulation of adhesion molecules on high endothelial venules that line arterioles ==> lymph nodes
Migration of naive T cells ==> nodes
Signal that lets T cells out of nodes is blocked
109
What are the secondary lymphatic organs?
Bone marrow, lymph nodes, spleen
110
What are the 2 effects of Tm cells?
High frequency
| Immediate effector function
111
What are the 2 effects of Bm cells?
High frequency
| Develop ==> plasma cells
112
What are the 3 features of memory plasma cells?
Secrete high affinity
Live for years
Protective immunity
113
What suffix describes inflammation?
-itis
114
What is inflammation?
Reaction of vascularised living tissue to local injury
115
How are injured tissue be repaired?
Regeneration if damaged parenchyma can divide + be replaced
| Fibroblastic/glial scar tissue
116
What are the 4 cardinal signs of acute inflammation?
Redness
Swelling
Heat
Pain
117
What are the 4 vascular changes in acute inflammation?
Transient vasoconstriction of arterioles
Vasodilatation and increased blood flow
Slowing circulation cos of increased permeability of microvasculature
Exudation of fluid + plasma proteins
118
What is acute serous inflammation?
Accumulation of fluid can be dominant feature of inflammation e.g. friction blister/burn
119
What is exudate?
Inflammatory extravascular fluid
| Increased protein content, much cellular debris
120
What is pus?
Purulent (thick) exudate rich in leukocytes (mostly neutrophils) + parenchymal cell debris
121
What is the name of the subcellular organelles within endothelial cells?
What do they respond to?
What do they release and what's contained within them?
Weibel-Palade bodies
His + thrombosis factors
Cell adhesion molecules + p selectin
122
When is p selectin released to the stimulation surface?
On stimulation with His complement C5a/LPS
123
How does expression of p selectin and e selectin on endothelium affect neutrophils?
Neutrophils in blood slow down by interacting with carb receptors + roll along endothelium
124
What is margination?
Increased adhesion of inflammatory cells to endothelium + rolling along endothelium
125
What is chemotaxis?
Unidirectional migration of cells towards a chemokine
126
What are the 3 main inducers of chemotactic agents for neutrophils?
Bacterial production
Component of complement system, partic C5a
Products of lipoxygenase pathway of arachidonic acid metabolism, partic leukotriene B4
127
What is diapedesis?
Movement across endothelium
128
What is acute suppurative inflammation?
Dominant accumulation of neutrophils, lots of pus
| e.g. acute appendicitus
129
What is acute fibrinous inflammation?
Inflammation of lung, fibrin + neutrophils
| e.g. lobar pneumonia
130
What is acute membranous inflammation?
Membrane forms over inflamed tissue
| e.g. pseudomembranous colitis
131
What is chronic granulomatous inflammation?
Presence of granulomas (macrophages that from spherical mass)
Attracted to chemokines from area of injury
132
What is an early granuloma?
Macrophage with a peripheral cuff of lymphocytes
133
What happens to an early granuloma in:
a) Non-infectious causes?
b) Infectious causes?
a) Produces non-caseating (non-infectious) epithelial granuloma,
b) Undergo central necrosis
Produce caseating epithelioid granuloma
Fibroblasts produce collagen, turn ==> scar in 8 weeks
134
What is a foreign body granuloma?
Giant cells can phagocytose large foreign material
| Birefringence on polarised light allows visualisation of foreign material
135
What is immediate hypersensitivity and what is it mediated by?
Allergy
| IgE, mast cells, Th2 receptors
136
What is atopy?
Inherited tendency to make immediate hypersensitivity response
30-50% of pop suffer
137
What is wheal + flare?
Raised lesion + surrounding redness
138
How does Th2 cause a direct allergic response?
Pollen grains uptaken by APC
Processed + presented as peptides which activates CD4 cells
Produces Th2 response where Th2 cytokines activate B cells
Differentiate ==> plasma cells that make IgE antibodies
Specific to pollen + binds mast cells in nose/skin/mucosal site
Any pollen binding to IgE activates mast cells, degranulates
139
What is immunological self tolerance?
Controlled failure to respond to self despite having capability to do so
140
What is autoimmunity?
Loss of immunological tolerance to self components
141
What is the spectrum of autoimmune disease?
Organ + non-organ specific
142
What is Grave's disease and what happens in it?
Autoimmune thyroid disease
Anti-TSH receptor binds to TSH receptor on thyrocyte
Maintains in ON position + makes unregulated thyroxine
Causes fast heartbeat, hyperactivity, weight loss, bulging eyes, goitre
143
What happens in myasthenia gravis?
Antibody AcH receptor + damages them, less available
Insufficient engagement with neuronal stimulus
X/little muscle contraction
Muscular weakness/fatigue
144
How is type 1 diabetes T cell mediated?
Supported by:
CD8 T cell mediated killing of B cells
CD4 T cell mediated inflammation
Failure of Treg to suppress
145
What are the 2 types of immunodeficiency?
Primary - inherited, rare
| Secondary - acquired, common
146
What is an example of primary immunodeficiency?
DiGeorge syndrome
Thymus x form so T cells x form
Abnormalities of heart + facial features, immunodeficiencies
147
What is an example of a secondary immunodeficiency and a possible therapy?
HIV
| HAART - Highly Active Antiretroviral Therapy
148
What 2 cells interact that can cause cancer?
Programmed Death -1 (PD-1)
Programmed Death Ligand 1 (PD-L1) on cancer cells blocks PD-1 so cell x die
MA produced can block interaction between 2
149
What is Post transplant lymphoproliferative disease? (PTLD)
B cells infected with Epstein-Barr virus
Cytotoxic T cells x control infection
B cells undergo malignant transformation + form B cell lymphoma
150
What 3 characteristics of bacteria are used for classification?
Morphological characteristics
Biochemical properties
DNA sequencing of genome
151
What 5 characteristics of viruses are used for classification?
```
Type of nucleic acid (DNA/RNA)
No of strand of nucleic acid (ss/ds) + physical construction
Polarity of viral genome
Symmetry of nucleocapsid
Lipid envelope
```
152
What are the 2 types of parasites?
Helminths
| Protozoa
153
What are helminths?
Multicellular worms that infect many organs of body
| Commonly GI tract
154
How does transmission of helminths occur?
Direct by swallowing larvae/larvae piercing skin
| Indirect via intermediate non-human host
155
What are protozoa and what is there life cycle?
Single cell organisms
Metabolically active growth stage (trophozoite)
Dorman stage (cyst)
156
How is infection via protozoa acquired?
Ingestion of contaminated H2O/food/via insect vectors
157
What are fungi?
```
Single cell (yeast) with branched filaments (hyphae)
Thick chitin cell wall
```
158
What stains are used in gram +ve and -ve bact?
Primary stain: crystal blue (violet)
Mordant (fixes dyes) - iodine
Decolonizing agent: alcohol/acetone
Counter stain: Safranin (red)
159
Why does gram -ve bact change colour more than gram +ve in staining?
Thin peptidoglycan layer
| X retain primary staining
160
What are 4 features of a bacterial capsule?
Gelatinous layer outside cell wall, composed polysac
Helps bacterial adherence
Antigenic - component of vaccine
Used for identification + lab diagnosis
161
What are 4 features of a bacterial flagella?
Organ of motility
Flagellated bact have fixed no + location of flagella
Role of pathogenesis
Used for identification + lab diagnosis
162
What 2 features of pili/fimbriae?
Hair-like filaments extend from cell surface
| Thinner + shorter than flagella
163
What are the 2 main functions of pili/fimbriae?
Attachment (normal ones)
| Conjugation (sex pilli)
164
What are 5 features of bacterial plasmids?
Additional extrachromosomal genetic material
Mostly circular dsDNA
Capable self replication
Can contain antibiotic resistance genes
Transmissible by conjugation, transduction/transformation
165
What bacteria produce spores?
| What special about species?
2 species of gram positive
Bacillus - aerobic
Clostridium - anaerobic
166
2 features of bacterial spores?
Highly resistant structures formed in response adverse conditions
Contain bacterial DNA surrounded by thick keratin like coat - resistance heat, chem, drying
167
How can you kill spores?
Resistant to boiling - killed by autoclaving 15' at 121 degrees
Only sporicidal solutions kills spores - bleach, other Cl based compounds
168
2 features of viral capsids?
Constructed from small no of virally encoded protein subunits - capsomeres
Viral genomes enclosed by capsid protein coat - nucleocapsid
169
3 types of symmetry virus particles show?
Icosahedral
Helical
Complex
170
2 features of icosahedral capsids?
20 equilateral triangles arranged around face of a sphere
| Simplest capsid 3 identical subunits - min is 60 subunits
171
2 features of helical capsids?
Genome wind ==> helix
| Symmetry only occurs in RNA viruses
172
2 features of complex capsids?
Pox viruses e.g. smallpox
| Nucleocapsid continuous cylinder surrounded by lipid layer + complex proteinaceous core wall
173
4 features of viral envelope?
Lipid bilayer derived from host cell membrane
X present in all viruses
Contain viral glycoproteins (spikes) that project from membrane
Interaction between capsid + envelope mediated by viral matrix protein
174
How is stability virus affected when it's:
a) Non-enveloped?
b) Enveloped?
a) Stable in environ, transmitted by food/H2O
| b) Survive transiently outside host + infectious disease persist in environ e.g. HIV
175
What is prion diease?
Proteinaceous Infectious Particle
Fatal + infectious neurodegenerative diseases
Misfolded protein alters folding of normal host version of protein
176
3 types of symbiotic associations?
Commensalism - 1 organism benefits, other X harm/benefit
Mutualism - benefit to both organisms involved
Parasitism - 1 organism (parasite) benefits at expense of other
177
What are the 2 types of parasites and how do they work?
Obligate - intracellular, only reproduce within host cells
Facultative - x rely on host to continue their life cycle
can live + reproduce inside + outside cells
178
3 functions of normal human flora?
Helps development of mucosal immunity
Protects host from colonisation mit pathogen microbes
Aids digestion of food
179
What type of flora is easily removed from by routine handwash?
Transient flora
180
What is the most common agent in:
a) Resident flora?
b) Transient flora?
a) Staph. epidermidis
| b) Staph. aures
181
Colonisation defintion?
New microorganism grows on superficial body sites without invading body
182
Definition of:
a) Sign?
b) Symptom?
c) Syndrome?
a) Objective manifestation of disease, observed + measured by others
b) Subjective features of disease experienced only by patient, infectious can be asymptomatic/symptomatic
c) Groups of symptoms + signs characteristics of a disease
183
4 stages of infectious disease progression?
Incubation - time between exposure + onset of specific clinical sign
Prodromal - Period where non-specific symptoms occur
Illness
Recovery (convalescence)
184
What are the 4 types of infections based on occurence?
Sporadic - occurs occasionally
Endemic - Continuously present in pop/community/country
Epidemic - Greater no of cases than normal in area within shrt period of time
Pandemic - epidemic disease with worldwide distribution
185
What are the 2 types of infections based on site of infection?
Superficial - Replication at epithelium at site of entry
Systemic - Replication at multiple sites, infection at deeper tissues
spread via lymph + blood
186
What are the 2 types of infection based in outcome?
Acute - rapid onset of disease, relativ brief period of symptoms, pathogen cleared in few days
Persistent - pathogen x cleared from host, remains in tissue
187
What are the 2 types of persistent infection?
Latent - microorganisms persist after initial disease, asymptomatic/symptomatic reactivation
Chronic - Continued production of infectious organism + immune evasion
188
What is nosocomial infection?
Any infection acquired in hospital/medical facility
| Affects patients + healthcare professionals
189
Why are nosocomial infections common?
Easily moved around by staff, patients, visitors
| X always prevented by hand washing
190
What molecules on bact bind to host cell receptors?
Adhesins
191
Host range defintion?
Diff species of hosts a given pathogen can infect
192
Tissue tropism definition?
Diff tissues within a given host that are infected by pathogen
193
Permissive cell defintion?
Allows pathogen to replicate
194
What enzymes do bacteria produce that allow them to spread to deeper tissues?
Collagenase + hyaluronidase - disrupt epithelial basal lamina
Coagulase - triggers formation of fibrin clot around bact, protect from phagocytosis
Leukocidins - degrade WBC
Hemolysins - degrade RBC
195
Pathogenicity definition?
Ability of microbe to cause disease
196
Virulence definition?
Degree of pathogenicity in a microorganism
197
What are the 3 bacterial virulence factors?
Adhesins + invasions
Endotoxins - LPS present cell wall of gram -ve (low toxicity)
Exotoxins - Secreted proteins produced gram +ve/-ve (high toxicity)
198
What are the 4 viral virulence factors?
Alter ability of virus to replicate
Modify host defence mechanisms
Enable virus spread in host
Act as toxic proteins
199
What are superantigens (SAgs)?
Toxins that stimulate immune system but x require processing to peptides
Bind to MHC-II molecules non-specifically + stimulate large no of T cells
e.g. Toxic Shock Syndrome Toxin 1
200
What is a reservoir (in terms of bact)?
Habitat where infectious agent normally grows, lives and multiplies
Usu from source which it's transmitted to a susceptible host
201
What are zoonotic diseases?
Spread between animals and peoples
202
What is an emerging disease?
Unrecognized infection/previously unrecognized infection that's expanded ==> new ecological niche
203
What are the 3 types of contact transmission?
Direct contact
Indirect contact - via non living object e.g. eating utensils
Droplet transmission - mucus droplets travel <1 m
204
What are 3 types of vehicle transmission?
H2O borne - H20 contaminated by sewage
Airborne - Inhalation of small pathogens + particles
Food borne - due bad sanitation
205
What are 2 types of vector transmission?
Mechanical - passive transport of pathogens on vector's body, flies most common
Biological - pathogen prt of life in vector + transmission to host through bite
206
What is:
a) Horizontal transmission?
b) Vertical transmission?
a) Person-person that's x mother + offspring
b) Transmission mother to child,
Occur in utero across placenta, delivery, breast
feeding
207
What are Koch's 4 postulates?
Microorganisms found in abundance in all suffering organisms but x healthy ones
Microorganism must be isolated from diseased organism + grow in pure culture
Cultured microorganism cause disease when introduced ==> healthy organism
Microorganism reisolated from inoculated, diseased experimental host + identical to orig specific causative agent
208
What are 3 exceptions to Koch's postulates?
Asymptomatic/subclinical infection carriers
Some microbes x grow in vitro
X all organisms exposed to infectious agent will acquire infection
209
What are the 3 types of direct methods of laboratory diagnosis?
Cultures of bact/viruses
Microscopy
Detection of nucleic acids
210
How are cultures of bacteria formed?
Propagated microorganisms by allowing them to grow in predetermined culture medium under controlled lab conditions
211
What is a colony?
Thousands of bact growing on surface that orginate from a single cell
212
4 types of medium bact can be grown in?
Defined medium - if exact chem composition known
Enrichment medium - contains component that supports growth of specific types/species bact
Selective medium - designed support growth of specific microorganism
Differential medium - distinguishes closely related microorganism growth on same media
213
How are cultures of viruses formed?
Propagation requires cell cultures
| Multiplicity of Infection (MOI) refers to no of virions added per cell during infection
214
How is detection of nucleic acids carried out?
Detect presence of bacterial + viral DNA/RNA in a patient specimen
Detect organisms slow/difficult to grow in laboratory
215
What is the indirect method of lab diagnosis?
Serological tests
| Presence of antibodies in serum/microbial antigens in tissue/bodily fluids
216
What is a titre?
Antibody conc in sample
| No of times can dilute a sample and still detect an antibody
217
How much more antibody must be present in acute sample compared to convalescence sample for a diagnosis to be made?
4 fold rise
218
Presence of what type of antibodies indicate an active infection?
IgM antibodies
219
What is the difference between:
a) Bactericidal?
b) Bacteriostatic?
a) Kill bact
| b) Inhibit growth of bact
220
What are the 3 main targets of antiviral agents?
Attachment + entry - inhibit fusion of viral envelope/attachment to receptos
Nucleic acid synthesis
Assembly + budding - inhibit viral proteins needed for virion mutation +/ release
221
What are 4 bacterial resistance strategies?
Reduce drug ability to penetrate cell
Inactivate drug
Expulsion of drug via general/specific efflux pumps
Modification of drug target site
222
What are 2 viral resistance strategies?
Error prone polymerase enzyme in RNA virus means develop resistance mehr than DNA viruses
Mutation within target of antiviral drug
