Theme 1b Cells of the Immune System

Question 1

What kinds of cells can Hematopoietic Stem Cells (HSC) differentiate into?
What is the process called?
Where does this differentiation originally occur in adult vertebrates?

Answer 1

HSCs can differentiate into all red and white blood cells in a process called “hematopoiesis”.
It occurs in the bone marrow

Question 2

What are the two major types of progenitor cells produced through hematopoiesis?

Answer 2

• Common myeloid progenitor cells
• Common lymphoid progenitor cells

Question 3

Are Leukocytes (WBCs) myeloid or lymphoid?

Answer 3

Trick question. They can be either

Question 4

What is a marker that can be used to identify all leukocytes?

Answer 4

CD45

Question 5

What are the 4 main types of cells which develop from common myeloid progenitors?

Answer 5

• Erythrocytes (RBCs)
• Granulocytes (Neutrophils, Basophils/ mast cells, Eosinophils)
• Monocytes
• Megakaryocytes

Question 6

Neutrophils
Functions?
% of WBC?
Life span?
Responds to what?
How many enter & leave circulation daily?

Answer 6

• phagocytose pathogens, release granules (cytokines and NETs)
• 50-70%
• 10hrs in circulation and 1-2 days in tissues
• Responds to early inflammation (first 4 hrs)
• ~100 billion enter and leave circulation /day

Question 7

What are NETs?

Answer 7

Neutrophil extracellular traps, cell release their DNA which stick to and immobilizes pathogens

Question 8

What are some molecules found in neutrophil granules? Give examples and functions.

Answer 8

• Proteases => Elastase, collagenase => tissue remodeling
• Antimicrobial proteins => Defensins, lysozyme => direct harm to pathogens
• Protease inhibitors => alpha1-antitrypsin => Regulation of proteases
• Histamine => vasodilation and inflammation.

Question 9

Basophils / Mast-Cells
Function?
% of WBCs
Lifespan?

Answer 9

• Mediate hypersensitivity and allergic responses through the production of histamine and cytokines
• <1% of WBCs
• hrs-days in circulation (Basophils) , months in tissues (Mast Cells).

Question 10

What are some molecules found in basophil and mast cell granules?

Answer 10

• Cytokines => IL-4, IL-3 => Modulate adaptive immunity
• Lipid mediators => leukotrines => Regulate inflammation
• Histamine => Vasodilation and smooth muscle activation.

Question 11

Eosinophils
Function?
% WBCs?
Lifespan?

Answer 11

• Binds Fc regions of antibodies to initiate antibody dependent degranulation (ADD) where the cells release cytotoxic proteins. They also produce cytokines during wound healing. They are also involved in parasitic infections
• 4-5% of WBCs (10-12% during a parasitic infection)
• ~2hrs in circulation, 8-12 days in tissues.

Question 12

What molecules are in Eosinophil granules?

Answer 12

• Cationic proteins => EPO (induces formation of ROS), MBP (vasodilation and basophil degranulation)
• Ribonucleases => ECP, EDN => antiviral activity
• Cytokines => IL=4, IL-10, IL-13, TNF-alpha => modulate adaptive immune response
• Chemokines => RANTES, MIP-1alpha =>Attract leukocytes

Question 13

Monocytes
Function?

Answer 13

• Migrate into tissues and differentiate into either macrophages or dendritic cells.
• macrophages repair /remodel, phagocytose pathogens, and present antigens to T-cells
• immature dendritic cells will capture antigens, then mature and migrate out of the tissue into the lymphoid organs where they present antigens to naive T-cells.

Question 14

Which do platelets lack: a nucleus or granules?

Answer 14

a nucleus, they release cytokines and growth factors.

Question 15

What are the most numerous cells in blood and what are their main function?

Answer 15

Platelets. They prevent bleeding though clotting.

Question 16

What are the three main types of cells that lymphoid progenitors differentiate into? and what percentage of WBCs do they account for?

Answer 16

• B lymphocytes
• T lymphocytes
• ILCs (innate lymphoid cells)

25% of all WBCs

Question 17

T-cells
Lifespan?
Site of Maturation?
Characteristic marker?

Answer 17

• weeks for Naive/ activated cell, years for memory cells.
• Mature in the Thymus
• CD3, is part of the TCR.

Question 18

What are the two types of T-cells?

Answer 18

• Cytotoxic T- cells: kill infected cells with lytic granules and are CD8+
• Helper T- cells: stimulate adaptive immune response through cytokine production and B-cell activation.

Question 19

B-cell
How are they activated?
Site of Maturation?
Lifespan?

Answer 19

• through binding to antigens and T helper cells.
• Bone marrow
• Weeks (naive/activated) years (memory)

Question 20

Innate Lymphocyte Cells
Function?
Lifespan?
Types?

Answer 20

• attack tumor cells and some virus infected cells. They have Fc receptors to bind antibodies which causes ADCC (antibody dependent cell cytotoxicity) or granules.
• weeks
• ILC1 (NK), ILC2, ILC3