Lecture 9.1: The Immunological Response

Question 1

Functions of the Immune System

Answer 1

• Defence against infections
• Defence against tumours
• Induce pathological inflammation
• Response to tissue grafts, newly introduced proteins

Question 2

Types of Immune Responses

Answer 2

Innate
Adaptive

Question 3

Types of Adaptive Immunity

Answer 3

Humoral
Cellular

Question 4

Innate immunity

Answer 4

• Fast
• Non-Specific
• Native, natural immunity
• Present from birth
• Involved in the triggering and amplification of adaptive immune responses
• Defences include release of cytokines, phagocytosis, production of
antibacterial peptides, activation of complement system

Question 5

Immune Effector Cells

Answer 5

White Blood Cells or Leukocytes
Monocytes
Lymphocytes
Granulocytes

Question 6

First Line of Defence: Epithelial Cells

Answer 6

• Mechanical, selective permeable barrier between the ‘outside’ and ‘inside’
• Produce antibacterial peptides e.g. defensins
• Produce cytokines and chemokines to attract and activate other cells
• Primary role is to block the entry of micro-organisms

Question 7

Secretory Molecules of the Innate System

Answer 7

• Transferrin/lactoferrin deprive microorganisms of iron
• Lysozyme breaks down bacterial cell wall (peptidoglycan) of gram +ve bacteria
• Complement components (directly with phagocytic cells)
• Opsonisation, chemotaxis and lysis of cells
• Antibody enhances the complement activation
• Cell lysis through perforins, create holes in the membrane

Question 8

Opsonisation

Answer 8

The coating of a microorganism by antibodies or complement to render it recognisable as foreign by phagocytes, thus enhancing phagocytosis

The membrane attack complex assembles to make a pore in the pathogen
membrane

Question 9

The Complement Cascade

Question 10

The 3 Stages of the Innate Immune Functions

Answer 10

• Recognition of microbes and damaged cells
• Activation of mechanisms
• Elimination of the unwanted substances

Question 11

Innate Immune Functions: Recognition

Answer 11

Uses pattern recognition receptors (PRRs) to recognize pathogen-associated
molecular patterns (PAMPs) and responds rapidly to invading pathogens

Activates other parts of the immune system and tissues throughout the body

Question 12

Cellular Responses

Answer 12

PAMPs (pathogen-associated molecular pattern):
• Molecular structures of microbial pathogen that required for survival

DAMPs (damage-associated molecular pattern):
• Result of cell damage by infections

Cellular receptors : PRRs (pattern recognition receptors)

Question 13

Cells of the Innate Immune System

Answer 13

• Phagocytes
• Neutrophils
• Macrophages and dendritic cells (from monocytes)
• (Eosinophils)

Question 14

Neutrophils

Answer 14

• 50- 70 % of circulating white blood cells
• Life span of 1-2 days
• Degranulation
• Exocytosis of granule contents into phagocytic vacuoles containing bacteria

Question 15

Macrophages

Answer 15

• Derived from monocytes
• 1-10% of circulating WBCs
• Phagocytose bacteria and damaged/unwanted cells
• Release cytokines
• Antigen presenting cells in adaptive immunity

Question 16

Steps of Phagocytosis

Answer 16

1) Macrophage recognises pathogenic antigen
2) Pathogen is engulfed by macrophage, in a phagosome via endocytosis
3) Phagosome combines with lysosome, becomes a phagolysosome
4) Lysozymes hydrolyse pathogen
5) Pathogen debris removed via exocytosis
6) Antigens may be presented on cell surface for adaptive immunity

Question 17

Monocytes: Dendritic Cells

Answer 17

• Dendritic cells act as the gateway to the adaptive response
• Roam freely throughout most tissues and organs
• Recognise and phagocytose pathogens
• Become effective antigen presenting cells
• Can secrete different cytokines by influencing lymphocyte differentiation and
maturation

Question 18

Eosinophils

Answer 18

• 1-3% of circulating WBCs
• Mainly in tissues
• Parasite response
• Allergic reactions
• Degranulation is main physiological mechanism
• Able to phagocytose materials in vitro

Question 19

Innate Responses

Answer 19

• Inflammatory Signalling (cytokines, plasma proteins)
• Increased blood flow to affected sites
• Phagocytosis
• Activation of the Adaptive Immune Response

Question 20

Co-Stimulation

Answer 20

Signals in addition to antigen that are needed to initiate adaptive responses