Overview of Immunology

Question 1

What is the definition of infectious diseases?

Answer 1

• Infectious diseases are caused by pathogenic microorganisms - such as bacteria, viruses, parasites, or fungi.
• The diseases can be spread, directly or indirectly, from one person to another.

Question 2

What are some examples of infectious diseases?

Answer 2

a. Influenza
b. Tuberculosis
c. Malaria
d. HIV/AIDs
e. COVID-19

Question 3

What are the common causes of morbidity and mortality?

Answer 3

Disorders of the immune system are common causes of morbidity and mortality.

Question 4

What are some examples of immune system disorders?

Answer 4

a. Autoimmune diseases – rheumatoid arthritis, lupus
b. Immunodeficiency disorders – HIV/AIDS, hypersensitivity reactions, allergies.

Question 5

What different types of pathogens does the immune system have to protect us against?

Answer 5

a. Viruses
b. Intracellular bacteria
c. Extracellular bacteria, Archaea, Protozoa
d. Fungi
e. Parasites

Question 6

How does bacteria multiply compare to viruses?

Answer 6

a. Bacteria - multiply by binary fission (a form of asexual reproduction)

b. Viruses – need to infect a host cell and hijack the host’s cellular machinery to replicate.

Question 7

In relation to host cells, where do viruses need to be to cause disease?

Answer 7

Viruses need to be inside host cells to cause disease.

Question 8

Where do bacteria need to be to cause disease and what mechanisms do they use?

Answer 8

a. Bacteria can cause diseases both inside and outside host cells.

b. Mechanisms used like toxins, enzymes, and cell invasion to cause harm.

Question 9

What are commensals?

Answer 9

a. Commensals are microorganisms that live in a symbiotic relationship with the host, often providing benefits without causing harm.

Question 10

What is a symbiotic relationship?

Answer 10

• A symbiotic relationship is a close, long-term interaction between two different species.
• It can be mutually beneficial (both species benefit) like bees and flowers, or harmful to one while benefiting the other, like parasites and their hosts.

Question 11

What are the different mechanical immune defences in the body?

Answer 11

a. Lysozymes in tears (and other secretions)
b. Commensals
c. Skin (physical barrier, fatty acids commensals)
d. Low pH in genitals (vagina for women)
e. Flushing of urinary tract
f. Rapid pH changes from gut to stomach.
g. Gut acid.
h. Bronchi – mucus, cilia
i. Removal of particles by rapid passage of air over turbinate bones.

Question 11

What are the different functions immune cells need to carry out?

Answer 11

a. Recognise infection by microbes.
b. Eliminate microbes and clear up damaged cells.
c. Remember previous infections.

Question 12

What are the two different organs of the immune system?

Answer 12

a. Primary lymphoid organs – Thymus, bone marrow

b. Secondary lymphoid organs – Waldeyer’s ring (tonsils and adenoids),

Bronchus-associated lymphoid tissue (mucus-associated lymphoid tissue MALT),

Spleen,

Lymph nodes,

Question 13

Define an antigen.

Answer 13

a. An antigen is a molecule that can be recognised by the immune system.
b. Usually, a protein or a polysaccharide.
c. Can trigger an immune response.

Question 14

Compare a human cell to a microbial cell.

Answer 14

a. Human cells – eukaryotic (true nucleus and membrane bound organelles) and complex.
b. Microbial cells – can be prokaryotic (bacteria, lack a true nucleus or any membrane bound organelles) or eukaryotic (fungi, protists), simpler in structure.

Question 15

What are soluble defences?

Answer 15

Soluble defences are immune defence mechanisms which are carried out by things floating in the blood.

Question 16

What are cellular defences?

Answer 16

Cellular defences are immune defence mechanisms which are carried out by cells directly interacting with each other.

Question 17

What defence mechanism’s do most immune responses use?

Answer 17

Most immune responses use a bit of both (soluble and cellular defence mechanisms), depending on the infecting organism, it will be mostly one or the other.

Question 18

What is humoral immunity?

Answer 18

Humoral immunity involves the production of antibodies by B cells to neutralise pathogens and toxins in the body fluids.

Question 19

What is cell-mediated immunity?

Answer 19

Cell mediated immunity involves the activation of T cells to directly attack infected or abnormal cells.

Question 20

What is innate immunity?

Answer 20

Innate immunity is the immediate, non-specific defence mechanism against pathogens.

It including physical barriers, phagocytes, and natural killer cells.

Question 21

What is adaptive immunity?

Answer 21

Adaptive immunity is a specific defence.

Mechanism involving the recognition of specific antigens and the development of immunological memory.

Question 22

How many hours after immune response, does innate immunity work for, and how many hours after immune response does adaptive immunity work for?

Answer 22

a. Innate immunity – works within first hours of infection.
b. Adaptive immunity – works after a few days but provides long-term protection.

Question 23

Describe the process of the innate immunity and adaptive immunity on a cellular level.

Answer 23

a. Innate immunity - physical barriers, phagocytic cells, and natural killer cells.

b. Adaptive immunity – B and T lymphocytes – which produce antibodies and directly kill infected cells, respectively.

Question 24

What mechanisms does the immune system have to protect against bacteria?

Answer 24

a. Immune cells can phagocytose bacteria, and antibodies can neutralise them.

b. Complement system can also enhance bacterial destruction.

Question 25

What is Phagocytosis?

Answer 25

Specialist cells engulf bacteria and break them down in special compartments containing enzymes and toxic free radicals.

Question 26

What is Opsonisation?

Answer 26

Helps phagocytic cells to pick up bacteria.

Question 27

What is neutralisation?

Answer 27

Stops bacteria from binding and colonising the tissue.

Question 28

What does ‘phage’ and ‘cyte’ refer to?

Answer 28

a. Phage – to eat.
b. Cyte – cell.

Question 29

What are DAMPs, MAMP’S and PAMP’s?

Answer 29

a. DAMPs – Damage-Associated Molecular Patterns.
b. MAMPs – Microbe-Associated molecular patterns.
c. PAMPs – Pathogen-Associated molecular patterns.
d. They are molecules recognised by the immune system, triggering responses to infection or tissue damage.

Question 30

What are chemokines and cytokines?

Answer 30

Chemokines:

Definition: Subset of cytokines guiding immune cell migration (chemotaxis).
Functions: Direct cells to sites of infection, inflammation, control immune cell activation.
Significance: Vital for immune surveillance, tissue repair; implicated in oral inflammatory diseases. Understanding chemokines (chemotaxis) is crucial in dentistry for managing oral inflammation and immune responses.

Cytokines:

Definition: Small signaling proteins in cell communication.
Functions: Regulate immune responses, inflammation, hematopoiesis (blood cell formation).
Examples: Interleukins, interferons, tumor necrosis factors (TNF), growth factors.
Significance: Crucial for immunoregulation; pivotal in dentistry for understanding immune responses during various oral conditions and procedures.

Question 31

What are the different types of Opsonin’s?

Answer 31

a. Opsonin’s are proteins which facilitate phagocytosis by binding to pathogens.
b. Making them more susceptible to engulfment by immune cells.
c. Immunoglobulins (antibodies) and complement proteins are opsonin’s.

Question 32

What is the structure of the Adhesion pili?

Answer 32

Adhesion pili structure

Question 33

What are exotoxins?

Answer 33

Exotoxins – toxic proteins released by certain bacteria into the surrounding environment, causing damage to host cells.

Question 34

What are aggressins?

Answer 34

Aggressins – bacteria virulence factors that enhance the ability of bacteria to invade and survive in host tissues.

Question 35

What are the different pathways for the initiation of complement activation?

Answer 35

a. Classical
b. Lectin
c. Alternative pathways
d. Can occur through any three of these pathways.
e. Leading to the formation of the membrane attack complex (MAC) that destroys pathogens.

Question 36

Describe the complement system simply.

Answer 36

a. The complement system – a group of proteins that enhance the immune response.
b. Leading to opsonisation, inflammation, and lysis of pathogens.

Question 37

What is agglutination?

Answer 37

a. Agglutination – clumping of particles.
b. Such as bacteria, by antibodies.
c. Enhancing their removal by phagocytes.

Question 38

Describe the cascade of events of inflammation (use the example of swelling).

Answer 38

1. Vasodilation and Increased Permeability:

Vasodilation: In response to injury or infection, blood vessels near the affected area dilate. This dilation increases blood flow, causing redness and warmth.
Increased Permeability: Blood vessel walls become more permeable, allowing proteins, immune cells, and nutrients to move from the bloodstream into the tissue. This influx of fluid and cells leads to swelling or edema.
2. Chemotaxis and Migration of Immune Cells:

Chemotaxis: Chemical signals (chemokines) attract white blood cells (e.g., neutrophils) to the site of inflammation.
Migration: Neutrophils move from the bloodstream to the tissue, guided by these chemical signals. They are among the first responders and play a key role in the initial immune response.
3. Phagocytosis and Release of Mediators:

Phagocytosis: Neutrophils engulf and digest bacteria, debris, and damaged cells through phagocytosis, helping to eliminate the cause of inflammation.
Release of Mediators: Immune cells release mediators such as cytokines and prostaglandins, which amplify the immune response and coordinate the activities of various cells.
4. Resolution and Tissue Repair:

Resolution: Anti-inflammatory signals prevail, leading to the resolution of the inflammatory response. Macrophages (another type of immune cell) play a key role in clearing debris and promoting tissue repair.
Tissue Repair: Fibroblasts and other cells are recruited to the site to repair the damaged tissue. In the case of dental injuries, this repair process is crucial for healing damaged oral tissues.

Question 39

Which mechanisms will be effective against viruses once they are inside?

Answer 39

a. Specialised T cells – like cytotoxic T lymphocytes, these recognise and kill infected cells.
b. Interferons – which can inhibit viral replication inside host cells.

Question 40

What are specialist cells?

Answer 40

Natural killer cells (NK-cells)

Question 41

Which mechanisms can specialist cells kill infected cells?

Answer 41

Specialised cytotoxic T cells can directly kill infected cells using perforin and granzyme granules.

Question 42

What is perforin and granzyme granules?

Answer 42

a. Perforin – creates pores in the target cell membrane.
b. Allowing Granzymes to enter and induce apoptosis (cell death) in the infected cell.

Question 43

What is apoptosis?

Answer 43

a. Apoptosis – programmed cell death.
b. A natural process in the body.
c. Crucial; for development, tissue homeostasis and removing damaged or infected cells.

Question 44

Within the oral cavity, what are the different immune defences?

Answer 44

a. Physical barriers – mucous membranes.
b. Saliva – with antimicrobial enzymes
c. Gingival Crevicular fluid
d. Lymphoid tissues

Question 45

What components does the process of saliva use?

Answer 45

a. Enzymes – e.g. lysozyme
b. Antibodies – e.g. IgA – that help in neutralising and clearing pathogens.

Question 46

What components does the process of Gingival crevicular fluid use?

Answer 46

The gingival crevicular fluid contains enzymes, antimicrobial agents, growth factors, metabolites, cells.

cytokines, chemokines, prostaglandins

enzymes: proteases, collagenases - tissue remodelling and breakdown of proteins.

AA - lysosomes and defensins - defend oral cavity

GF - EGF (epidermal growth factors)

Question 47

What components does the Lymphoid tissues use?

Answer 47

1. Lymphocytes: Lymphoid tissues are primarily composed of specialized white blood cells called lymphocytes. There are two main types of lymphocytes: B cells (responsible for antibody production) and T cells (involved in cell-mediated immunity).
2. Antigens: Antigens are molecules or particles (such as bacteria, viruses, or foreign substances) that trigger an immune response. Lymphocytes recognize antigens and respond to them by producing antibodies (B cells) or by attacking infected cells directly (T cells).
3. Dendritic Cells: These specialized cells in lymphoid tissues capture antigens and present them to lymphocytes, initiating immune responses.
4. Lymphatic Vessels: Lymphoid tissues are connected by a network of lymphatic vessels, which transport lymph (a clear fluid containing white blood cells) throughout the body. Lymph carries antigens and lymphocytes, facilitating their interactions.
5. Bone Marrow: Lymphocytes are produced and mature in the bone marrow. B cells mature into specialized cells capable of producing antibodies, while T cells mature into various subsets with specific immune functions.
6. Thymus: The thymus is an organ where T cells mature and differentiate into different T cell types with specific roles in the immune response.
7. Spleen: The spleen filters blood, removing damaged blood cells and pathogens. It also serves as a reservoir of lymphocytes and initiates immune responses against blood-borne infections.