Midterm Part 1

Question 1

Which cells stem from the MCP?

Answer 1

monocytes (that mature into macrophages),
mast cells, and
granulocytes (neutrophils, basophils, and eosinophils).

Question 2

Which cells stem from the CLP?

Answer 2

cytotoxic T cells (CTLs),
T helper (Th) cells,
T regulatory (Treg) cells,
B cells.

Question 3

What are cytokines?

Answer 3

• Soluble, secreted proteins of the immune system (interleukins)
• Chemical messengers produced by immune and non-immune
  cells to regulate immune cell development and function

Question 4

Where are DC’s derived from?

Answer 4

Some types are derived from the CMP, some from the CLP

Question 5

What are the primary lymphoid organs, and what is their function

Answer 5

The place where developing lymphocytes mature:

the bone marrow (the center part of the long bones), and
the thymus (a flat, bi-lobed organ that is situated above your heart).

Question 6

What is the function of secondary lymphoid organs are what are they?

Answer 6

• place where mature lymphocytes encounter pathogens or foreign molecules and where adaptive immune responses begin
• The spleen and the lymph nodes

Question 7

What is lymph?

Answer 7

It is like blood, but no RBCs or platelets

Question 8

What is an example of a physical and a chemical barrier that acts as a first layer of defence?

Answer 8

Physical: skin (dry and high salt environment)
Chemical: HCL in stomach, lysozyme in sweat and tears, lactic acid in vagina

Question 9

After a pathogen breaks through the first layer of defence, what innate immune responses happen within MINUTES?

Answer 9

• compliment activation

- macrophages phagocytose the pathogen

Question 10

After a pathogen breaks through the first layer of defence, what innate immune responses happen within HOURS?

Answer 10

• increased vasodilation, increased vascularity, recruitment of opsonins (leaky and sticky blood vessels)
• Recruitment of more phagocytic cells (neutrophils and monocytes) to
  engulf and kill the pathogen. The changes in the blood vessel allow
  these cells to leave the blood and enter the tissue

Question 11

Where do B cells mature?

Answer 11

In the bone marrow

Question 12

?Where do T cells develop/mature? Where do they migrate after that?

Answer 12

In the thymus, in the secondary lymphoid organs

Question 13

What happens if your spleen is removed?

Answer 13

• When the spleen is surgically removed, some of its
  functions are taken over by the bone marrow and liver;
  other functions are simply absent, and the body manages
  without them
• People without spleens are prone to systemic bacterial
  infections

Question 14

What circulates through the lymph? (Options: erythrocytes, platelets, leukocytes)

Answer 14

Leukocytes (WBC)

Question 15

Does lymph enter the spleen?

Answer 15

No

Question 16

How are immune responses to tissue-borne infections initiated?

Answer 16

When naïve cells and lymph meet in lymph nodes,

pathogens can be detected

Question 17

What are the five types of Pathogen Associated Molecular Patterns?

Answer 17

1. are not produced by the multi-cellular host organism,
2. are shared by large groups of pathogens,
3. do not undergo frequent mutation,
4. are often essential for pathogen’s survival, and
5. are recognised by PRRs in the innate response.

Question 18

What are the two main groups of Pathogen Recognition Receptors?

Answer 18

1. phagocytosis receptors (that are used to bring the particle inside the phagocyte) and
2. Toll-like Receptors (TLRs, to allow the phagocyte to determine if the particle is dangerous, i.e., a pathogen).

Question 19

What is the structure of TLR?

Answer 19

• an extracellular leucine-rich domain that recognises the PAMP,
• a transmembrane domain,
• cytoplasmic domain that is homologous to the IL-1 receptor (a receptor that binds the cytokine, interleukin-1 (IL-1)

Question 20

What is the classical pathway? (Complement)

Answer 20

complement proteins are activated when antibodies made during a previous adaptive immune response bind to the pathogen surface

Question 21

What is the alternate pathway?

Answer 21

• complement proteins bind directly to the bacteria and initiate the complement activation cascade directly (does not need antibodies)
• There is alot of c3 in blood, so the reaction can happen spontaneously

Question 22

Explain how the complement cascade goes

Answer 22

The C3 convertase cleaves additional C3 into C3a and C3b; after binding, C3b recruits additional proteins to form the enzyme complex C5 convertase that cleaves C5 into C5a and C5b

Question 23

What is the function of C3 convertase and C5 convertase?

Answer 23

• C3 convertase breaks down the protein C3 into C3a and C3b

- C5 convertase breaks down the protein C5 into C5a and C5b

Question 24

What is the function of C3a and C5a?

Answer 24

• increases permeability of the blood vessels and induces the expression of adhesion molecules that allow leukocytes such as neutrophils and monocytes to attach to the blood vessels (leaky and sticky)
• bind to receptors on the resident mast cells and resident macrophages to release additional histamine (C5a) and TNF-α (C3a)
• C5a: chemoattractant of neutrophils and monocytes

Question 25

What is the function of C3b?

Answer 25

Opsonization (sticks to pathogen and gets macrophage to eat it)

Question 26

What is opsonization?

Answer 26

• alteration of the pathogen surface or particle surface so that phagocytic cells can engulf it more efficiently (fork helps you eat your food more easily)

Question 27

What is the function of C5b?

Answer 27

Sticks to the cell and initiates forming the MAC (punches hole through the cell)

Question 28

What is the function of TLR? Where are they found?

Answer 28

• Toll-like receptors (TLRs) are a type of PRR that allow innate cells of the immune system to identify something as dangerous to the host.
• the plasma membrane of cells as well as endosomal membranes.