HD3: Natural history of infection Flashcards
Relevant part of immunology of stage 2 basically
Koch’s postulates:
The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
The microorganism must be isolated from a diseased organism and grown in pure culture.
The cultured microorganism should cause disease when introduced into a healthy organism.
The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
What’s the biggest change between the old and current koch’s postulates?
nucleic acid sequence presence is looked at instead pathogen presence thanks to development of PCR
What are the modern Koch’s postulates:
A nucleic acid sequence belonging to a putative pathogen should be present in most cases of an infectious disease. Microbial nucleic acids should be found preferentially in diseased organs known, and fewer/not in those organs that lack pathology.
With resolution of disease, the copy number of pathogen-associated nucleic acid sequences should decrease or become undetectable. With clinical relapse, the opposite should occur.
Where sequence detection predates disease, copy number correlates with severity of disease or pathology, there is more likely to be a causal relationship.
The nature of the microorganism should be consistent with the known biological characteristics of that group of organisms.
These sequence-based forms of evidence for microbial causation should be reproducible.
What’s the difference between primmary and opportunistic pathogens?
Primary Pathogens
Cause disease in non-immunocompromised host
Opportunistic: Often commonly found pathogens. Only cause infection in damaged host
Give examples of what may allow an opporunistic pathogen infection?
Immunosupressed- chemotherapy, age, alcohol, infection (e.g. HIV, TB),diet.
Tissue damage- trauma, burns, radiation.
Catheter infections
Genetic defects
Change in host bacteria e.g. antibiotics, diet
What 3 things do primmary pathogens do to a healthy host cause disease?
Intrinsic virulence
Toxin production
Induction of abnormal host response
What is cellulitis?
Cellulitis (sel-u-LIE-tis) is a common, potentially serious bacterial skin infection. The affected skin appears swollen and red and is typically painful and warm to the touch. Cellulitis usually affects the skin on the lower legs, but it can occur in the face, arms and other areas
Droplet e.g. Influenza, rhinovirus, TB Sexually e.g. HIV, syphillis Blood- e.g. HBV, HIV, HCV. Bites- anaerobic infection, HBV, Rabies Give 3 further modes of transmission:
Feacal-oral e.g. salmonella, noravirus
Enviromental e.g. C.difficile,strongyloides, enterovirus
Vector bourne through lice, ticks, fleas, sandfly, mosquitos, tsetse fly.
What is the term used to describe that bacteria are able to regulate gene transcription and thus phenotype based upon their enviroment/medium (population density around them). The bacteria must possess three characteristics: to secrete a signaling molecule, an autoinducer, to detect the change in concentration of signaling molecules, and to regulate gene transcription as a response.[2] This process is highly dependent on the diffusion mechanism of the signaling molecules. QS Signaling molecules are usually secreted at a low level by individual bacteria. At low cell density, the molecules may just diffuse away. At high cell density, the local concentration of signaling molecules may exceed its threshold level, and trigger changes in gene expressions
quorum sensing
What are the 2 methods bacteria attach to host:
adherence though bacteria adhesions and host receptors
AND
biofils (attachment and intracellular adhesions)
One example f adhesins interacting with host receptor is: interacting in fimbria salmonella.
what adhesin does HIV use to target CD4 T cells?
2) what are the major cellular targets for HIV-1?
3) where are they found?
CD4 with gp120 HIV protein
2) CD4 lymphoctyes (GI tract and other tissues, 1% in circulation) and macrophages (all tissues and lymphatic system)
What can make pathogens more virulent:
Ability to replicate within the host
Toxin production-
Cell death-
Survival with eukaryocytic cells.
How can cell death make pathogen’s virulent
HIV and CD4 cells, apoptosis, direct toxicity on cells by pathogen (HCV) or immune system (HBV
What are the 2 ways toxins can be encoded? give 2 examples of each toxin:
Plasmid encoded- TSST, Tetanus neurotoxin
Phage encoded- Cholera Toxin, diptheria toxin.
what is a granuloma:
A granuloma is a structure formed during inflammation that is found in many diseases. It is a collection of immune cells known as macrophages.
What are the 3 types of immune invasion:
passive, active, aggressive
give 3 characteristics of passive immune evasion:
Latency e.g. herpes, Malaria
Can hide in sanctuary sites
Resistance to phagocytosis and destruction by lysosymes
give 3 characteristics of active immune evasion:
Production of immunomodulatory proteins
Decoy
Evolution
give 3 characteristics of aggressive immune evasion:
Counterattack on immune system e.g. HIV
Bacteria:
a) pro or eu -karyotic?
b) single or multi cellular?
c) organelles membrane or non-membrane bound?
d) sexual or asexual reproduction (+term given)
1) pro
b) pro
c) non-mem
d) asexual (binary fission)
gram negative are purple or pink?
pink
gram positive are purpleor pink?
purple
According to class 1 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:
dsDNA - mRNA (herpes)
According to class 2 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:
ssDNA -dsDNA -mRNA (parvovirus)
According to class 3 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:
dsRNA- mRNA (rotavirus)
According to class 4 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:
(+) ssRNA- (-)ssRNA- mRNA
hepatitisi C virus
According to class 5 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:
(-)ssRNA- mRNA
Rabies
According to class 6 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:
(+)ssRNA- DNA/RNA hybrid- dsDNA- mRNA
HIV
According to class 7 of the baltimore classification system, what form doe the virus store its genetic material + 1 e.g.:
dsDNA- ssRNA- mRNA
HBV
Fungal infections
1) eukaryotes or pro?
2) how do yeasts replicate?
3) ow do moulds replicate?
4) which method of replication is asexual?
5) what is the role of septae in fungus?
6) single or multicellular?
1) eukaryotes
2) mitosis
3) meiosis
4) mitosis is sexual, meiosis is asexual
5) septae is the cell membrane, it divides what would be a multinuclear fungus into many cells, it is relatively fluid
6) both
Protozoa
a) single or multicellular?
b) motile or no?
a) Single cell organisms
b) Very motile
Can protozoa encyst?
yes
Protozoa, true or false
can engulf food
c)True: Can engulf food
Protozoa, true or false
won’t survive hostile intracellular
d) False: Often survive hostile intracellular environmen
Protozoa
method of reproduction?
e)Asexual and sexual reproduction
Parasites
a) single or multicellular?
complex multicellular
PARASITE
DESCRIBE RELA. WITH HOST
symbiotic
Parasites often have a life cycle outside of host
true or false
true
What are the 2 ways parasites cause disease?
Direct tissue damage
- Immunological reaction to parasite.
Which host defence method is missing:
1) skin and membranes with commensal bacteria
2) complement- help fight bacterial infections
3) phagocytois by neutrophils and macrophages
4) cytokines
5) innate immunity and humoral immunity
secretions
Which host defence method is missing:
1) skin and membranes with commensal bacteria
2) secretions
3) phagocytois by neutrophils and macrophages
4) cytokines
5) innate immunity and humoral immunity
complement- help fight bacterial infections
Which host defence method is missing:
1) complement- help fight bacterial infections
2) secretions
3) phagocytois by neutrophils and macrophages
4) cytokines
5) innate immunity and humoral immunity
skin and membranes with commensal bacteria
Which host defence method is missing:
1) complement- help fight bacterial infections
2) secretions
3) skin and membranes with commensal bacteria
4) cytokines
5) innate immunity and humoral immunity
phagocytois by neutrophils and macrophages
Which host defence method is missing:
1) complement- help fight bacterial infections
2) phagocytois by neutrophils and macrophages
3) skin and membranes with commensal bacteria
4) secretions
5) innate immunity and humoral immunity
cytokines
what is the difference between cell-mediated and humoral immunity?
Humoral immunity secretes antibodies to fight against antigens, whereas cell-mediated immunity secretes cytokines and no antibodies to attack the pathogens.
What is the innate immune response comprise of?
the basic bitches, the ones at the front of the que. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body.
What are the innate immune system cells?
Natural killer cells, mast cells, eosinophils, basophils; and the phagocytic cells include macrophages, neutrophils, and dendritic cells,
what happens after a non-specific innate immune response?
the adaptive immune repsonse
Which immunoglobulin is involved in the innate immune response?
IgA
Is this part of the innate or adaptive immune response:
Recruitment of cells of innate immune cells through cytokines (such as histamine,
prostoglandins e.t.c)
innate
Is this part of the innate or adaptive immune response:
Complement- opsinisation, chemoattraction direct effect against Bacteria
innate
Is this part of the innate or adaptive immune response:
Recognition of pathogens through antigen presentation
adaptive
Is this part of the innate or adaptive immune response:
Antigen presentation
innate
Is this part of the innate or adaptive immune response:
Specific activation of specialised cells
adaptive
Is this part of the innate or adaptive immune response:
Development of ‘memory’ to allow quick recognition of pathogen in future
adaptive
Which is the innate and whic is the adaptive immune response:
antigen presentation followed by the recognition of presented antigen leading to activation of specialised lymphocytes through
the antigen presentation is done by innate immune cells, (but can also be done by adaptive)
the recognition and activation part is the adaptive immune respone
What MHC class (the molecule of the antigen presenting cell or infected target cell that holds the presented antigen) does the folllowing interact with and thus cause activation of:
a) CD4+ T cells
b) CD8+ T cells
a) MHC class 2
b) MHC class 1
To present the antigen on an MHC class 2 molecule, how does the antigen presenting cell process the antigen?
exogenous pathway
To present the antigen on an MHC class 1 molecule, how does the antigen presenting cell process the antigen?
endogenous pathway
If an infected target cell e.g. a macrophage, is presenting an antigen on the MHC class 2 which will the result be: b) What type of immunity is this?
1) activation of CH4+ T cell (Th1 cell)
2) release of cytokine: IFN-gamma
3) Enhanced opsonisation of bacteria/viruses (often intracellular) through B cell
antibody production.
b) cell-mediated immunity
If an infected target cell e.g. a macrophage, is presenting an antigen on the MHC class 1 what will the result be: b) What type of immunity is this?
1) activation of CH8+ T cell (Th2 cell)
2) release of cytokines (interferon gamma, TNF-alpha), and cytolytic effects of infected cell (perforin (to puncture), granzymes, Fas ligand)
b) cell-mediated
What is the name given to this response:
1) activation of CH4+ T cell
2) release of cytokine: IFN-gamma
TH 1 response
What is the name given to this response:
1) activation of CH8+ T cell (Th1 cell)
2) release of cytokines (interferon gamma, TNF-alpha), and cytolytic effects of infected cell (perforin (to puncture), granzymes, Fas ligand))
TH 1 response
Which cells can produce MHC class 2 ?
professional antigen presenting cells e..g dendritic cells, mononuclear phagocytes
Which cells can produce MHC class 1 ?
all
What is the effect of IL-4 on T helper cells:
1) if the T helper cell is CD8, will have no affect
2) if the T helper cell is CD4 then will become a type 2 CD4 helper T cell, otherwise IL-2 will stimulate it to become a type 1 CD4 T helper cell
what is the main cytokine of the cell mediated response?
interferon-gamma,(then I’d say IL-2 has a big role in proliferating CD 4 type 2 and CD 8 T cells)
What are the cells involved in the cell mediated immune response:
1) APCs are highly specialized dendritic cells
2) Th0
3) Th CD8
4) Th2 CD4
5) Memory T cells
Main differences between TH2 and TH1 response:
TH1 is cell mediated immune response characteristed by interferon-gamma and is part of the cell mediated immune response (despite that IFN-g is part of the inducing of B cells to make antibodies).
TH2 response is part of the humoral immune response (therefore involves antibodies in fluid) and is characterised by the cytokine IL-4
what does IFN-gamma do?
IFN-g
a) activates the bactericidal activities of macrophages
b)induces B cells to make opsonizing (marking for phagocytosis) and complement-fixing antibodies,
= cell-mediated immunity.
What does IL-4 do?
1) stimulation of activated B-cell and T-cell proliferation,
2) differentiation of B cells into plasma cells.
3) induces B-cell class switching to IgE,
What immune response is more effective against extracellular infections
humoral immune response with a TH 2 response
What immune response is more effective against toxins
humoral immune response with a TH 2 respons
What immune response is more effective against intracellular infections
cell mediated immune response with a TH1 response e.g. CD8+ T cells cytolytic effects
Give the causes of immunodeficiency:
Caused by infection e.g HIV
Poor diet/alcohol
Genetic e.g. complement deficiency, CGD,
Splenic dysfunction (sickle cell disorder)
Age
Other diseases e.g. diabetes, cancer
