Immunology Lecture 26+27

Question 1

Learning objectives

Answer 1

Aims
To provide an introduction into the basic concepts of immunology and provide an
overview of how dysfunction of the immune system can lead to disease and
conversely how understanding immunology has revolutionised modern medicine
Learning Objectives
● Understand the difference between innate, adaptive and passive immunity

● Describe the roles of B and T cells

● Describe the role of the different components of the immune system

● Understand how dysfunction of the immune system can lead to disease

● Understand how understanding immunology has revolutionised modern
medicine.

Question 2

Define immunity

Answer 2

The state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease

Question 3

List some examples of first line defences (6 points)

Answer 3

● Skin
● Tears
● Cilia and mucus
● Stomach acid
● Urine flow
● Friendly bacteria

Question 4

How does skin act as a first line of defence against pathogens?

Answer 4

Acts as physical barrier

Question 5

How do tears act as first line of defence

Answer 5

Tears contain lysozyme enzymes which can break down bacterial cell walls

Question 6

How do cilia and mucus act as a first line of defence?

Answer 6

Mucus can trap bacteria/fungi/pathogens. Cilia actively beat which moves the mucus lining our bronchioles up into the throat, where the mucus is swallowed and any pathogens in the mucus are killed by acids in the stomach

Question 7

How does the stomach act as a first line of defence?

Answer 7

Low pH, contains hydrochloric acid which can kill pathogens. Proteases e.g. pepsin can be activated in the stomach, killing pathogens

Question 8

How does urine flow act as a first line of defence?

Answer 8

●urine flow helps flush out pathogens from the urinary tract

Question 9

How do ‘friendly bacteria’ form a first line of defence?

Answer 9

●Friendly bacteria e.g. those on our skin or in our stomach are naturally occurring and form a microbiome which acts as competition to reduce ability of pathogens to colonise and grow

Question 10

Which type of immunity is classed as first line of defence?

Answer 10

Innate Immunity

Question 11

What is the function of innate immunity?

Answer 11

innate immunity provides a quick and nonspecific defense against a variety of pathogens, creating barriers, using cellular components, and initiating inflammatory responses to prevent or limit infections

Question 12

Compare and contrast innate immunity, adaptive immunity and passive immunity.
(Specificity, Timing, Memory, Components)

Answer 12

Specificity:

● Innate immunity is nonspecific.
●Adaptive immunity is highly specific.
●Passive immunity can be specific if it involves the transfer of antibodies with defined specificities.

Timing:

●Innate immunity provides immediate, rapid defense.
●Adaptive immunity has a delayed response.
●Passive immunity provides immediate but temporary protection.

Memory:

●Innate immunity lacks memory.
●Adaptive immunity has immunological memory.
●Passive immunity does not confer memory.

Components:

●Innate immunity involves physical barriers, phagocytes, and the complement system.
●Adaptive immunity involves B cells, T cells, antibodies, and memory cells.
●Passive immunity involves the transfer of antibodies.

Question 13

What are the 2 main types of hematopoietic cells?
Which immunity is each one involved in?

Answer 13

Myeloid cells - innate immunity
lymphoid cells - adaptive immunity

Question 14

What are PAMPs

Answer 14

Molecules associated with pathogen infection that act as ligands for Toll-like Receptors/ TLRs.

TLRs detect infection and initiate the immune response

Question 15

What is the function of TLRs?
Where can they be found/expressed?
What does it mean when you said TLRs are expressed somewhere?

Answer 15

Function - detection of infections and the initiation of mainly the innate immune response but also influence adaptive immune response

Expressed - expressed on the surface of various immune cells e.g. B cells dendritic cells, macrophages and neutrophils (all myeloid cells)

Means that is where they can be found. Expressed on neutrophils, dendritic cells and macrophages = you will find TLRs on the outer membranes of these cells

Question 16

What are some of the main myeloid (involved in innate immunity) cells?

Answer 16

Dendritic cells

neutrophils

macrophages

Question 17

What is the purpose of TLRs in innate immunity?

Answer 17

TLRs have recognition sites on their extracellular domains which bind DAMPs and PAMPs.

TLRs know something has bound to them via internal signalling pathway that ultimately changes cell behaviour and gene expression for pro inflammatory cells

Question 18

What myeloid cells are TLRs expressed by / found on the outer membrane of?

Answer 18

Dendritic cells, neutrophils, macrophages

Question 19

In innate immunity, what happens when cells recognise PAMPs? What are some of the outcomes?

Answer 19

When cells involved in innate immunity (such as dendritic cells, macrophages and neutrophils) recognise PAMPs, they are activated. The cells then secrete ligands which attract additional cells involved in innate immunity

After this, the inflammatory response can be triggered as well as
- Further release of pro-inflammatory cytokines
- Fever, which inhibits pathogen proliferation

Question 20

What are the 3 main specialist phagocytic cells recruited in innate immunity?
State some details about them.
(macrophages, neutrophils, eosinophils)

Answer 20

Neutrophils - short lived, abundant in blood but not in tissue, respond and migrate to sites of infection

Macrophages - long lived, abundant in areas likely to be exposed to pathogens e.g. lungs and gut

Eosinophils - specialists in attacking objects too large to engulf

Question 21

What are some of the functions of dendritic cells? 3 points

Answer 21

• express large variety of recognition receptors e.g. TLRs
• phagocytoses pathogens
• migrate to lymphoid tissues and activate and stimulate T-cells of the adaptive immune system

Question 22

What type of cells are involved in adaptive immunity?

Answer 22

Lymphocytes

Question 23

What is needed to activate T cells?

Answer 23

APCs, usually dendritic cells.
dendritic cells have a role in phagocytosis, antigen capture, antigen processing, antigen presentation

Question 24

What are the 2 main types of lymphocytes?

Answer 24

B - Cells mature in bone marrow
T - Cells mature in Thymus

Question 25

chatgpt What are B cells and T cells?
what are they
function
memory
location

Answer 25

B cells + T cells are two major types of lymphocytes, a type of white blood cell crucial for the immune system. Both B cells and T cells play key roles in adaptive immunity, providing specific and long-lasting protection against pathogens.

Function:

B Cells:
- primarily responsible for antibody-mediated immunity
-produce antibodies that can recognize and neutralize pathogens
- can differentiate into plasma cells

T Cells:
- involved in cell-mediated immunity, involving direct cellular responses against infected or abnormal cells.
- T cells can directly kill infected cells or regulate immune responses
- T cells recognize antigens presented on the surface of other cells.
- Helper T cells recognize antigens on the surface of APCs,
- cytotoxic T cells directly recognize antigens on infected cells

Memory:

B Cells:
- B cells generate memory B cells during an immune response. Memory B cells “remember” the specific antigens encountered, allowing for a faster and more effective response upon subsequent exposure to the same pathogen.

T cells:
- T cells generate memory T cells during an immune response. Memory T cells contribute to the long-term immune memory allowing for a faster and more effective response upon subsequent exposure to the same pathogen

Location:
B cells mature in bone marrow
T cells mature in the thymus

Question 26

What is the name for the first branch of lymphocyte from the common lymphoid progenitor? What is their function?
(Natural killer cells are part of innate immunity)

Answer 26

Natural Killer Cells
Function - Participate in early defence against foreign cells and autologous cells undergoing stress e.g. microbial infection or tumour transformation

Question 27

What are the 3 subtypes of T-cells?

Answer 27

Cytotoxic t-cells = kill infected host cells

Helper t-cells - activate macrophages, dendritic cells, b cells and cytotoxic t-cells by secreting cytokines and displaying co-stimulatory proteins on their surface

Regulatory t-cells = inhibit other t-cells

Question 28

how does adaptive immunity work? (6 points)

Answer 28

Body randomly generates a collection of lymphocytes, most of which are dormant

- When an antigen is presented (e.g. by dendritic cells or t-helper cells) to dormant lymphocytes, those with binding affinity to the antigen activate

- Binding of antigen to activated lymphocytes leads to proliferation and clonal expansion Expansion triggers differentiation into effector cells

- An expansion round occurs every time an antigen is encountered

- Subsequent encounters stimulate memory cells made from previous encounter - this time a bigger pool of cells will be able to bind

Body can respond to multiple antigens at once

Question 29

Give 3 examples of modern medicines created through the understanding of immunology.

Answer 29

Cancer vaccines - direct immune response designed to prevent specific cancer epitopes and cancer causing pathogens

oncolytic viruses - lab modified viruses that can infect and kill certain tumour cells

CAR T-cell therapy:
- Take T-cells from PT and infect them with recombinant virus that causes expression of a TCR with an antigen binding domain specific to a tumour antigen
- This generates T-cells able to attach to specific tumour cells, which are transfused back into the PT

Question 30

Give an example of a disease caused by dysfunction in the immune system (HIV)

Answer 30

• virus which infects T-helper cells, dendritic cells and macrophages expressing CD4 receptor
• infected immune cells no longer function and trigger t-helper cells to target cells required for adaptive immunity
• results in immune deficiency leading to infections and cancers not normally seen in those with healthy immune systems