Immunology Overview

Question 1

Physical and chemical barriers to infection

Answer 1

skin

mucosa

• Resp
• GI
• Genital urinary

Chemical barriers

• Hydrochloric acid
• Lysozyme (Sweat and tears)

Question 2

Initial response to pathogen invading tissue

Answer 2

1. Complement system activation:
   - Membrane attack complex destroys pathogen
   - C3b is an opsonin
   - C5a attracts cells (neutrophils, monocytes and eosinophils)
   - C3a,C4a and C5a activate mast cell degranulation
   - C3a and C5a activate eosinophil degranulation
2. Macrophages recognise pathogen and activate innate immune system
3. Dendritic cells pick up antigens and begin activating the specific immune system

Question 3

How do macrophages recognize pathogens?

Answer 3

By binding to pathogen associated molecular patterns (PAMPs)

Macrophage uses various receptors such as toll like receptors

Question 4

Phagocytosis

Answer 4

Done by macrophages and neutrophils (both phagocytes)

Wraps pathogen in cell membrane creating a phagosome -> phagosomes bind with lysosomes which provide digestive enzymes

If macrophage can’t deal with pathogen alone - will release cytokines (signalling proteins_

Question 5

Cytokines

Answer 5

Signalling proteins that lead to inflammation

Leads to recruitment of:

• Macrophages
• Monocytes
• Neutrophils

+ inflammatory response

Question 6

Monocytes

Answer 6

Precursors to macrophages that float around in the blood

• Differentiate into macrophages once they enter tissues

Question 7

Neutrophils

Answer 7

Another type of phagocyte that circulates in blood and can enter the tissues to destroy pathogens – more specific to bacterial infection

Question 8

Inflammatory response: (generalised)

Answer 8

• Vasodilation
• Increased vascular permeability
• Mast cell activation and degranulation (releasing further cytokines)
• Activation of clotting system
• Activation of kinin system

Question 9

Interleukins

Answer 9

Type of cytokine that is released by macrophages and neutrophils – leading to systemic inflammatory response

Question 10

IL-1

Answer 10

sent to brain to signal fever, reduced apetite and lethargy

Question 11

IL-6

Answer 11

Sent to liver to prodice Acute phase proteins – act as Opsonins

Question 12

IL-8

Answer 12

Recruits and activates more neutrophils

Question 13

IL-2/IL-12

Answer 13

Activates Natural Killer Cells

Question 14

TNF-α

Answer 14

Does all of IL-1/6/8/2/12 effects

Question 15

Opsonins

Answer 15

Complex molecules that attach to pathogens and help macrophages and neutrophils to identify them
- Promote phagocytosis

= Example of an opsonin is CRP

Question 16

CRP

Answer 16

Produced by liver in response to IL-6

Good marker of inflammation/ infection

Question 17

Complement System

Answer 17

Involves various C1-9 proteins that activate eachother in the complement cascade

• Various products of the complement cascade result in
  = Opsonins
  =Inflammation
  = Destroying pathogens

Question 18

3 ways of activating complement cascade

Answer 18

1. Lectin Pathway
2. Alternative Pathway
3. Classical Pathway

1+2 - activated directly by pathogens

3 - activated by antibody-antigen complexes (arising from specific immune system)

Question 19

T + B Cells

Answer 19

Both types of lymphocytes

Comprise the specific immune system

Free to float in blood + lymphatic system
but most are concentrated in:
= Lymph nodes
= mucosa associated lymphoid tissue

Question 20

Dendritic cells

Answer 20

Antigen presenting cells that travel from site of infection through blood and lymphatics to lymph nodes
- Activates T and B cells

Question 21

What do dendritic ells present antigens on

Answer 21

HLA Class II molecules

Question 22

CD4 Cells

Answer 22

Type of T cell

Activated by antigens on dendritic cells (HLA Class II)

Proliferate to become T-Helper Cells

Question 23

T Helper cells

Answer 23

1# Present antigens on their HLA Class I molecules
- Recognised by CD8 Cells (another type of T Cell)

2# Also release cytokines responsible for:
= making CD8 cells proliferate and differentiate into cytotoxic T cells
= B Cells into proliferating and differentiating into 1# Plasma cells and 2# memory B cells

3# Travel to site of infection and release cytokines responsible for recruitment of monocytes and macrophages to the active tissue

Question 24

CD8 Cells

Answer 24

Activated by:

• T- Helper cells presenting antigens (HLA Class I)
• Cytokines released by T-Helper cells

Once activated:
- proliferate and differentiate into Cytotoxic T-Cells

Question 25

Plasma cells

Answer 25

Differentiated from B cells in response to cytokine activation from T-Helper cells

Responsible for making large numbers of antibodies

Question 26

Cytotoxic T- Cells

Answer 26

Responsible for killing cells that have been infected by pathogens
- Such as virally infected cells

Question 27

How do Cytotoxic T-Cells promote cell death:

Answer 27

Attach themselves to the infected cells with T-cell receptor to HLA Class I molecule presenting antigen on infected cell

Kill Via 2 methods:
1# Granule exocytosis
2# Activate FAS Molecule (apoptosis)

Question 28

Actions of antibodies

Answer 28

1. Attach to toxins and neutralise toxic effects
2. Attach to the receptors of viruses and bacteria - prevent them from carrying out their function
   = e.g. stop viruses from recognising cells that it will invade
3. Agglutination:
   = Clumping together of pathogens
4. Act as highly specific opsonins