Session 5 Lecture Notes

Question 1

What are healthcare infections?

Answer 1

Infections arising as a consequence of providing healthcare (can be in patients, visitors or staff)

Question 2

How many hours after a patient is admitted is an infection considered a healthcare infection?

Answer 2

If the patient presents symptoms 48 hours after admission

Question 3

What is the largest type of healthcare acquired infection?

Answer 3

Gastrointestinal

Question 4

Give some examples of healthcare acquired infections caused by viruses

Answer 4

1. Blood borne viruses (HIV, HEP B and C)
2. Norovirus
3. Chickenpox
4. Influenza

Question 5

Give some examples of healthcare acquired infections caused by bacteria

Answer 5

1. Staph aureas
2. C. Difficile
3. E. coli
4. Mycobacterium tuberculosis

Question 6

Give some examples of healthcare acquired infections caused by fungi

Answer 6

1. Candida albicans

2. Aspergillus species

Question 7

Give an example of a healthcare acquired infection caused by parasites

Answer 7

Malaria

Question 8

What are the 4Ps of infection prevention and control?

Answer 8

1. Patient
2. Pathogen
3. Practice
4. Place

Question 9

Have you I-fived your patients today? The 5 Is in infection prevention and control are?

Answer 9

1. Identify
2. Isolate
3. Investigate
4. Inform
5. Initiate

Question 10

What is the only way in which the T cells are activated?

Answer 10

By an antigen presenting cell

Increasing T cell numbers of increasing levels of the pathogen will have no effect with APC activation

Question 11

The immune system can recognise 2 types of microbes - what are they?

Answer 11

1. Extracellular microbe (they divide outside the cell)

2. Intracellular microbe (they divide inside the cell - mostly viruses)

Question 12

Give some examples of where APCs are located

Answer 12

At the main points of entry:

1. Skin
2. Mucous membranes
3. Lymph organs eg lymph nodes and spleen
4. In the blood

Question 13

Name 4 types of APCs

Answer 13

1. Dendritic cells
2. Macrophages
3. Langerhans cells
4. B cells

Question 14

What is a naive T cell?

Answer 14

A mature T cell that has not yet encountered an antigen

Question 15

Where are Langerhans APCs found and what do they present to?

Answer 15

On the skin

Present to naive T cells

Question 16

Where are dendritic cells found?

Answer 16

In the lymph nodes
Mucous membranes
Blood
Present to naive T cells

Question 17

Where are macrophages found and what do they present to?

Answer 17

In tissues

Present to effector T cells (i.e. activates T cells)

Question 18

Where are B cells found and what do they present to?

Answer 18

Lymphoid tissues

Present to naive T cells and effector T cells

Question 19

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?

Answer 19

Extracellular = humoral immunity (antibodies, complement and phagocytosis)
Intracellular = cell mediated immunity (cytotoxic T cells, antibodies and macrophages)

Question 20

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?

Answer 20

MHC proteins
Major histocompatability complex
Also known as HLA

Question 21

There are 2 classes of MHC - what are they are where are they found?

Answer 21

Class 1 = on surface of all nucleated cells

Class 2 = on surface of macrophages, dendritic cells and B cells

Question 22

What types of microbes do class 1 and 2 cells present?

Answer 22

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

Question 23

There are 3 types of MHC class 1 molecules. What are they?

Answer 23

HLA-A
HLA-B
HLA-C

Question 24

There are 3 types of HCA class 2 molecules. What are they?

Answer 24

HLA-DR
HLA-DQ
HLA-DP

Question 25

Which chromosome is the MHC gene found on?

Answer 25

Chromosome 6

Question 26

MHC class 1 present which type of antigen and to which type of T cells?

Answer 26

Class 1 present intracellular microbes to CD8+ T cells

Question 27

MHC class 2 present which type of antigen and to which type of T cells?

Answer 27

MHC class 2 present extracellular microbes to CD4+ T cells

Question 28

What type of MHC molecules do dendritic cells contain?

Answer 28

``` Class 1 AND Class 2 Only dendritic cells, macrophages and B cells contains class 2 But also all nucleated cells contain class 1 ```

Question 29

Which are the only MHC molecules class that activates a humeral immune response? Via which T cells?

Answer 29

``` Class II (found on APCs) Activate CD4+ T cells and a humeral response ```

Question 30

What does APCs have cross presentation mean?

Answer 30

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

Question 31

Where are TCR produced and matured?

Answer 31

T cell receptors (found on surface of T cells) are produced in the bone marrow and mature in the thymus

Question 32

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?

Answer 32

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

Question 33

Following activation of CD4+ T cells there are 3 different T helper responses that can be mounted - what are they?

Answer 33

TH1 TH2 TH17

Question 34

Activated T cells secrete what 2 enzymes that help kill an infected cell?

Answer 34

``` Perforin = creates a perforin pore in the cell membrane Granzyme = starts the apoptotic process ```

Question 35

What T helper cells are activated when infection by intracellular microbes and which by extracellular microbes?

Answer 35

``` Extracellular = TH2 and TH17 Intracellular = TH1 ```

Question 36

What are the most important antibodies involved in allergic reactions

Answer 36

Immunoglobulin E

Question 37

What antibodies are produced in the 1st encounter with a pathogen and which are produced the 2nd time you encounter the same pathogen?

Answer 37

1st time = IgM | 2nd time = IgG

Question 38

What is an isotype switch?

Answer 38

When the B cells change the antibodies they are producing to one that is more effective (i.e. IgM to IgG)