Nature of Immunity

Question 1

What are the 4 types of pathogens?

Answer 1

Bacteria, Viruses, Fungi, Parasites (e.g protozoa & worms)

Question 2

What are the requirements of an effective immune response?

Answer 2

• Diverse nature of pathogens - range of defense mechanims
• vast range of pathogens - vast range of antigen receptors
• Rapid growth of microbes - rapid inflammatory response
• Minimise damage to host - there are regulatory mechanisms

Question 3

What does an immune response to infection involve?

Answer 3

1. Recognition - to locate and identify the pathogen
2. Defence - to repel or destroy the pathogen

Question 4

What are the important features of the immune system?

Answer 4

• Specificity - to each pathogen
• Memory - to create a 2nd immunological faster resposne
• self - discrimination - shouldn’t destroy self-tissue

Question 5

What are the levels of defense against pathogens?

Answer 5

• Physical barriers e.g skin, nails, GI tract, mucosal surfaces
• Innate immunity - rapid response to foreign cells
• Adaptive immnity - more specific

Question 6

How can pathogens get through the skin?

Answer 6

by wounds, burns, an insect injecting

Question 7

What are the cells involved in innate immunity?

Answer 7

1. Mast
2. Dendritic
3. Macrophage
4. NK
5. Complement protein
6. Granulocytes
7. Basophil, eosinophil, neutrophil

Question 8

What cells are involved in adaptive immunity?

Answer 8

1. gamma-delta (also innate)
2. NK T cell (also innate)
3. B cell
4. Antibodies
5. T cells (CD4 & CD8)

Question 9

What are the types of pathways in the complement system?

Answer 9

1. Classical - Antibody binds to specific antigen on pathogen surface
2. Lectin - Mannose-binding lectin binds to pathogen surface
3. Alternative - Pathogen surface creates local environment that’s helpful to complement pathway

Question 11

What events happen once Complement is activated?

Once one of pathways have been used

Answer 11

Step 1. After whichever pathway is used, complement is activated
Step 2. C3b covalently binds to surface components of pathogen
Step 3. (Classical - recruitment of inflammatory cells) (Lectin - Opsonisation of pathogens, facilitating uptake, & killing by phagocytes) (Alternative - Perforation (hole) pathogen cell membrane
Step 4. Death of pathogen

Question 12

What are the roles of neutrophils, macrophages, and mast cells?

White blood cells

Answer 12

• Neutrophil - circulates in the bloodstream before being recruited into tissues
• Macrophages - Wait in tissues before being activated to engulf the pathogen
• Mast cells - generate inflammation to help immune system fight the pathogen

Question 13

What is the difference between phagocytosis & pinocytosis?

Answer 13

• Phagocytosis engulfs the whole pathogen into a phagosome
• but in pinocytosis, small fragments are engulfed into a vesicle

Question 14

What is the process of phagocytosis?

PAMP = Pathogen Assosciated Molecular Patterns
PRR = Pathogen Recognition Receptors

Answer 14

1. chemotaxis - movement of phagocytes towards the pathogen
2. Adherance using PAMP recognition
3. Cell is activated using PRRs
4. Phagocytosis is initiated
5. phagosome and phagolysosome is formed
6. pathogen is killed and digested
7. degradation products are released from the cell

Question 15

Innate immune response

What happens at the site of infection?

Answer 15

1. Surface wound introduces bacteria, activating resident effector cells to secrete **cytokines **
2. There’s vasodilation and increased vascular permeability (allowing fluid, protein & inflammatory cells to go from blood into tissue)
3. Infected tissue becomes inflammed, causing redness, heat , swelling & pain

Question 16

Why does it take longer for adaptive immunity to be activated compared to innate?

Answer 16

Information about the pathogen has to be taken to the adaptive by the innate, through the lymph nodes in the lymphatic system

Question 17

What are the types of adaptive immunity?

Answer 17

• Cell-mediated (involves CD8+ cytotoxic T cells, and CD4+ T helper cells)
• Humoral (involves B cells that produce antibodies)

Question 18

What is the difference between B-cell receptor & T-cell receptor?

Answer 18

B-cell receptor can directly bind to antigen whereas T-cell receptor needs to have info presented to it

Question 19

What are the main differences between the innate & adaptive immunity?

Answer 19

• Defense: generic (innate) specific recognition (adaptive)
• Recognise structures: common characteristics of pathogens (innate) specific antigens on pathogens (adaptive)
• Immune cells used: already inherited collection (innate) generated collection (adaptive)
• Speed: quickly activated (innate) slow activation but faster on 2nd exposure (adaptive)
• Efficiency: moderate (innate) very (adaptive)