PMI02-2002 Introduction to host defence

Question 1

What is the immune system?

Answer 1

A communication network of cells and chemical signals distributed in blood and tissues which regulates normal growth and development of the organism while protecting against disease

Question 2

Where do B cells stem from?

Answer 2

Bone marrow

Question 3

Where do T cells stem from?

Answer 3

Thymus

Question 4

What occurs at secondary lymphoid sites?

Answer 4

Lymphocytes interact with each other to generate an immune response

Question 5

What is the difference between innate and adaptive immunity?

Answer 5

Innate is non-specific, has no memory and is immediate

Adaptive is specific, has memory and its effects are delayed

Question 6

What organisms is adaptive immunity restricted to?

Answer 6

vertebrates

Question 7

What are antibacterial peptides secreted by?

Answer 7

epithelial cells

Question 8

How do antibacterial peptides kill cells?

Answer 8

Damage the microbial cell wall

Question 9

Why do epithelia secrete mucus?

Answer 9

Microbes find it harder to adhere to surfaces

Flow of mucus washes microbes away

Question 10

What are the three pathways of the complement system?

Answer 10

Classical pathway
MB-Lectin pathway
Alternative pathway

Question 11

What is opsonisation?

Answer 11

The process by which a pathogen is marked for ingestion and destruction by a phagocyte

Question 12

What does complement activation lead to?

Answer 12

Recruitment of inflammatory cells
Opsonisation of pathogens
Killing of pathogens

Question 13

Which phagocytic cells circulate in the blood only?

Answer 13

Monocytes and neutrophils

Question 14

What phagocytic cells circulate in tissues only?

Answer 14

Macrophages

Question 15

What phagocytic cells circulate in blood and tissues?

Answer 15

dendritic cells

Question 16

Summarise phagocytosis

Answer 16

Phagocytes are recruited to the site of the infection by chemokines
Phagocytes bind to the pathogens
Phagocytosis occurs
Phagosome fuses with a lysosome to form a phagolysosome
Pathogen dies from reactive oxygen and nitrogen produced by the lysosome

Question 17

What cells bridge the gap between innate and adaptive immunity?

Answer 17

Dendritic cells

Question 18

What is the purpose of dendritic cells in bridging innate and adaptive immunity?

Answer 18

They capture microbes and take it to lymph nodes to induce adaptive immunity

Question 19

What initially occurs when dendritic cells engulf the microbes?

Answer 19

Processing
The microbes are digested into small peptide fragments
Presentation

Question 20

What molecules are antigens presented on?

Answer 20

MHC Class I molecules

MHC Class II molecules

Question 21

What pathogens are presented on MHC class I molecules?

Answer 21

Internal pathogens or viruses

Question 22

What pathogens are presented on MHC class II molecules?

Answer 22

external pathogens or bacteria

Question 23

Where does the MHC/ antigen complex go after it is formed?

Answer 23

Taken to the surface of the dendritic cell and presented to T cells

Question 24

Which cells do MHC class I induce?

Answer 24

CD8+ T cells (cytotoxic T cells)

Question 25

Which cells do MHC class II induce?

Answer 25

CD4+ T cells (T helper cells)

Question 26

How do dendritic cells enter the lymph node?

Answer 26

Via the afferent lymphatic vessel

Question 27

Where do dendritic cells activate T cells?

Answer 27

In the paracortical area of lymph node

Question 28

Where do dendritic cells activate B cells?

Answer 28

In the germinal centre of the lymph node

Question 29

Where do T and B cells gather and leave the lymph node?

Answer 29

Through the efferent lymphatic vessel

Question 30

How does Th0 produce 4 different Th cells?

Answer 30

Through the secretion of different cytokines

Question 31

What occurs when things in the immune system go wrong?

Answer 31

Microbes are too advanced for the immune system (Virus can hide inside cells eg: HIV)
Cancers growing unchecked (normal signals for cell growth or death fail)
Harmless substances are deemed dangerous (allergies)
Autoimmune system attacks itself (diabetes, rheumatoid arthritis)