Lecture 2 - Innate Immunity

Question 1

1. How are Pathogens Detected by the Innate Immune System?
2. What does detection Trigger (2 Examples)?

Answer 1

1. Receptors on the surface of Phagocytic and Epithelial Cells
2. Initiates Inflammatory Responses (e.g., Downstream Clotting, Tissue Repair Processes)

Question 2

Define the Two Major Types of Phagocytic Cell

Answer 2

• Macrophages = tissue-resident phagocytes (e.g., Connective Tissue, Brain)
• Neutrophils = short-lived phagocytes abundant in the blood, which are recruited to site of infection

Question 3

How is Inflammation Defined?

(4 Points)

Answer 3

• Dolor (Pain) - accumulation of fluid and plasma proteins in tissue
• Rubor (Redness) - increased blood flow
• Calor (Heat) - increased blood flow
• Tumor (Swelling) - accumulation of fluid and plasma proteins in tissue

Question 4

How is Inflammation Initiatied?

Answer 4

Rapid production of Cytokines and Chemokines by Macrophages in response to pathogens

Question 5

What are the Two Main Classes of Inflammatory Mediators? Give Examples of Each

Answer 5

1. Lipids (e.g., Prostaglandins, Leukotrienes) - produced by macrophages, alter cell behaviour
2. Proteins (e.g., Cytokines, Chemokines) - produced by various cell types, involved in both innate and adaptive immune responses

Question 6

What are the Two Pro-enzyme Cascades Activated by Wounding?

Answer 6

1. Kinin System - Plasma Proenzyme Cascade, which triggers the release of inflammatory mediators e.g., Bradykinin
2. Coagulation System - leads to formation of Fibrin Clot

Question 7

Define Pattern Recognition Receptors (PRRs). Give Two Examples

Answer 7

• Receptors found on/within Immune cells with broad specificity for pathogen molecules, recognising pathogen associated molecular patterns (PAMPs)
• Mannose-Binding Lectin (MBL), Toll-like Receptors (TLRs)

Question 8

How does Activation of PRRs lead to an Immune Response?

Answer 8

Activation leads to production of chemokines, cytokines and cell surface receptors via activation of Transcription Factors

Question 9

How can (i) Cytokines and (ii) Chemokines trigger an inflammatory response?

Answer 9

(i) Macrophage-produced cytokines cause dilation of local blood vessels and increased expression of adhesion molecules
(ii) Chemokine concentration gradient directs Leukocyte migration to the site of infection by Chemotaxis

Question 10

Define the 3 Steps of Phagocytosis

Answer 10

1. Recognition and Attachment of Particle to be ingested
2. Engulfment and Formation of a Phagocytic Vacuole
3. Killing/Degradation of ingested material

Question 11

Give 3 Examples of Toxic Products produced by Phagocytes to Kill Engulfed Pathogens

Answer 11

• Superoxide Anion - generated by NADPH Oxidase in a process known as a Respiratory burst
• Nitric Oxide
• Hydrogen Peroxide

Question 12

How are Killed Microorganisms Degraded?

Answer 12

Lysosomal Hydrolases