Session 5 Lecture Notes Flashcards
What are healthcare infections?
Infections arising as a consequence of providing healthcare (can be in patients, visitors or staff)
How many hours after a patient is admitted is an infection considered a healthcare infection?
If the patient presents symptoms 48 hours after admission
What is the largest type of healthcare acquired infection?
Gastrointestinal
Give some examples of healthcare acquired infections caused by viruses
- Blood borne viruses (HIV, HEP B and C)
- Norovirus
- Chickenpox
- Influenza
Give some examples of healthcare acquired infections caused by bacteria
- Staph aureas
- C. Difficile
- E. coli
- Mycobacterium tuberculosis
Give some examples of healthcare acquired infections caused by fungi
- Candida albicans
2. Aspergillus species
Give an example of a healthcare acquired infection caused by parasites
Malaria
What are the 4Ps of infection prevention and control?
- Patient
- Pathogen
- Practice
- Place
Have you I-fived your patients today? The 5 Is in infection prevention and control are?
- Identify
- Isolate
- Investigate
- Inform
- Initiate
What is the only way in which the T cells are activated?
By an antigen presenting cell
Increasing T cell numbers of increasing levels of the pathogen will have no effect with APC activation
The immune system can recognise 2 types of microbes - what are they?
- Extracellular microbe (they divide outside the cell)
2. Intracellular microbe (they divide inside the cell - mostly viruses)
Give some examples of where APCs are located
At the main points of entry:
- Skin
- Mucous membranes
- Lymph organs eg lymph nodes and spleen
- In the blood
Name 4 types of APCs
- Dendritic cells
- Macrophages
- Langerhans cells
- B cells
What is a naive T cell?
A mature T cell that has not yet encountered an antigen
Where are Langerhans APCs found and what do they present to?
On the skin
Present to naive T cells
Where are dendritic cells found?
In the lymph nodes
Mucous membranes
Blood
Present to naive T cells
Where are macrophages found and what do they present to?
In tissues
Present to effector T cells (i.e. activates T cells)
Where are B cells found and what do they present to?
Lymphoid tissues
Present to naive T cells and effector T cells
When PRRs recognise PAMPs on the pathogen they know they are either intracellular or extracellular pathogens. 2 different immune responses are created - which are they?
Extracellular = humoral immunity (antibodies, complement and phagocytosis) Intracellular = cell mediated immunity (cytotoxic T cells, antibodies and macrophages)
What antigen is present on the surface of cells, recognised by APCs and allowing for a cell mediated response to be activated if bound to a pathogen?
MHC proteins
Major histocompatability complex
Also known as HLA
There are 2 classes of MHC - what are they are where are they found?
Class 1 = on surface of all nucleated cells
Class 2 = on surface of macrophages, dendritic cells and B cells
What types of microbes do class 1 and 2 cells present?
MHC class 1 (found on all nucleated cells) = present INTRACELLULAR microbes MHC class 2 (found on macrophages, dendritic cells and B cells) = present EXTRACELLULAR microbes
There are 3 types of MHC class 1 molecules. What are they?
HLA-A
HLA-B
HLA-C
There are 3 types of HCA class 2 molecules. What are they?
HLA-DR
HLA-DQ
HLA-DP
Which chromosome is the MHC gene found on?
Chromosome 6
MHC class 1 present which type of antigen and to which type of T cells?
Class 1 present intracellular microbes to CD8+ T cells
MHC class 2 present which type of antigen and to which type of T cells?
MHC class 2 present extracellular microbes to CD4+ T cells
What type of MHC molecules do dendritic cells contain?
Class 1 AND Class 2 Only dendritic cells, macrophages and B cells contains class 2 But also all nucleated cells contain class 1
Which are the only MHC molecules class that activates a humeral immune response? Via which T cells?
Class II (found on APCs) Activate CD4+ T cells and a humeral response
What does APCs have cross presentation mean?
They have Class I and Class II molecules
All nucleated cells have Class I but only APCs have Class II which allows them to activate CD8+ T cells and for them to become cytotoxic T cells
Where are TCR produced and matured?
T cell receptors (found on surface of T cells) are produced in the bone marrow and mature in the thymus
In order for APCs to fully activate a TCR they require a co-stimulatory signal. What is this and what is the other signal they require?
APCs need to activate CD4+ T cells via Class II MHC molecules
In order to do this they require a costimulatory signal - CD28 on the TCR to be activated by CD80/86 on the APC
Following activation of CD4+ T cells there are 3 different T helper responses that can be mounted - what are they?
TH1
TH2
TH17
Activated T cells secrete what 2 enzymes that help kill an infected cell?
Perforin = creates a perforin pore in the cell membrane Granzyme = starts the apoptotic process
What T helper cells are activated when infection by intracellular microbes and which by extracellular microbes?
Extracellular = TH2 and TH17 Intracellular = TH1
What are the most important antibodies involved in allergic reactions
Immunoglobulin E
What antibodies are produced in the 1st encounter with a pathogen and which are produced the 2nd time you encounter the same pathogen?
1st time = IgM
2nd time = IgG
What is an isotype switch?
When the B cells change the antibodies they are producing to one that is more effective (i.e. IgM to IgG)
