Immune defences against infection

Question 1

What are physical barriers to pathogens?

Answer 1

Skin - fatty acids help to act as a barrier and we have natural commensals.
Mucus membrane - traps bacteria, allows us to cough it up or swallow and digest.

Question 2

What are antimicrobial peptides(AMPs)?

Answer 2

made by most animals, non- specific but form pores in bacteria causing water to flood in and burst the bacteria.

Question 3

What are antibacterial enzymes?

Answer 3

Lysozymes - in tears, destroys bacterial peptidoglycan layer.
Secretory phospholipase A2 - breaks down phospholipid layer in bacteria.
tears, saliva and phagocytes

Question 4

Why do the antibodies need recognise pathogens?

Answer 4

Antibodies need to discriminate between the self and non-self.

Question 5

What are pathogen recognition receptors (PRR)?

Answer 5

Located on macrophages, neutrophils and dendritic cells. Through the lock and key mechanism they can identify pathogens and recognise simple molecules and regular patterns.

Question 6

What are Toll-like receptors? (PRR)

Answer 6

Located on the membrane surface (inner or outer). There are 10 in the body that recognise different specific motifs.

Question 7

What are NOD-like receptors? (PRR)

Answer 7

Stands for nucleotide oligomerisation domains. They are intracellular.

Question 8

What are pathogen associated molecular patterns (PAMPs)

Answer 8

These are recognised by the TLRs. They are components of a pathogen that are not on or in the host cell. They can include mannose-rich oligosaccharides, peptidoglycans, lipopolysaccharides and unmethylated CpG DNA.

Question 9

What is haematopoiesis?

Answer 9

Platelets, WBCs (leukocytes) and RBCs all are generated from the bone marrow from haematopoietic stem cells. HSC can either go into a lymphoid or a myeloid progenitor. The lymphoid means the stem cells will become B, T or NK cells; and the myeloid will produce granulocytes and platelets.

Question 10

What are leukocytes?

Answer 10

They are WBCs. They include:
- lymphocytes (B, T, NK)
- monocytes (in blood)/ macrophages (in tissue)
- Granulocytes (neutrophils, eosinophils and basophils)

Question 11

What are cellular defences against pathogens?

Answer 11

Phagocytes (neutrophils and macrophages) for internal killing.
Extracellular killing
* goal is inflammation*

Question 12

What can an issue with phagocytes cause?

Answer 12

• bacterial infections (staphs and pseudomonas)
• fungal infections ( aspergillus and candida, or chronic granulomatous disease CGD)
• recurrent infections

Question 13

What are the main phagocytic cells?

Answer 13

Neutrophils and macrophages/ monocytes

Question 14

What is the process of phagocytosis?

Answer 14

1. Recognition and binding of the pathogen.
2. Internalisation (endocytosis) - enclosing the pathogen in an internal vacuole (phagosome).
3. Phagosome fuses with a lysosome to form a phagolysosome, the lysosome releases into the vacuole.
4. Kills pathogen and the digested products are released.

Question 15

What is extracellular killing?

Answer 15

On organisms that are to large to be phagocytosed. Cells involved are eosinophils and NK T cells.

Question 16

What are natural killer cells (NK)?

Answer 16

Come from the lymphoid progenitor. They contain lots pf granules and enzymes granzyme and perforin which are potent. They recognise something different and automatically attack it. They lack antigen specific receptors, and will just attack whatever is foreign. Made by some cytokines.

Question 17

What are cytokines?

Answer 17

Link the 2 arms of the immune system. Secreted by cells that stimulate or inhibit the activity, proliferation of differentiation of other cells.