Hematopoiesis

Question 1

What does myeloid tissue mean?

Answer 1

Tissue that is related to the bone marrow

Question 2

What is lymphoid tissue?

Answer 2

Tissue that is related to the lymphatic system (lymph nodes, thymus, spleen)

Question 3

Within the bone marrow, progenitor cells either belong to the ____ or ____ family lineage

Answer 3

Myeloid

Lymphatic

Question 4

Which cells arise from myeloid lineage?

Answer 4

Granulocytes, monocytes, erythroids, megakaryocytes/platelets

Question 5

Which cells arise from lymphoid lineage?

Answer 5

Lymphocytes and plasma cells

Question 6

How does maturation of lympohid cells differe from myeloid cells?

Answer 6

Myeloid cells mature in peripheral blood, lymphoid cells mature in lymphoid tissues before entering peripheral blood

Question 7

Within the myeloid lineage of bone marrow HSC, how are the types of cells further divided?

Answer 7

Into series

• myeloid series (granulocytes)
• Monocytic series (monocytes)
• Erythroid series (erythrocytes)
• Megakaryocytic series (platelets)

Question 8

What is a normal ratio of #myeloids : #erythroids?

Answer 8

2 or 3 : 1

Question 9

What is the myeloid organ?

Answer 9

bone marrow

Question 10

What is the difference between bone marrow core biopsy and bone marrow aspirate?

Answer 10

Aspirate does not contain any bone spicules, taken by aspirating bone marrow using 11G needle.

Question 11

• Other than hematopoetic stem cells, what other class of stem cells are in bone marrow?
• What effect do MSCs have on HSCs?

Answer 11

• Mesenchymal stem cells that ultimately become Bome Marrow Stromal Cells (chondrocytes, osteoblasts, adipocytes, endothelial cells. etc)
• They influence HSC behavior

Question 12

Are most stem cells quiescent or actively dividing?

Answer 12

Quiescent

Question 13

Once an HSC has been activated, what 3 outcomes are available to it?

Answer 13

Apoptosis

Self-renewal (proliferation)

Differentiation (progenitor for myeloid or lymphoid)

Question 14

What signals drive an HSC to become a myeloid progenitor cell?

Answer 14

SCF

TPO

Question 15

What signal drives an HSC to become a lymphoid progenitor cell?

Answer 15

Interleukin - 7

Question 16

What affect does injury have on HSCs in bone marrow?

Answer 16

It results in a shift towards differentiation to generate more progenitors to keep up with homeostasis

Question 17

What signaling molecule promotes differentiation from a myeloid progenitor to megakaryocytes-erythroid precursor?

Answer 17

IL-3

Question 18

What signaling molecule promotes megakaryocyte-erythroid precursor to become platelet? To become erythrocyte?

Answer 18

Platelet - TPO

Erythrocyte - EPO

Question 19

Describe how RBCs appear during staining from early differentiation to late differentiation.

Answer 19

More blue at beginning, more orange at end due to increased presence of Hb

Question 20

_____ are the largest cells in the marrow

Answer 20

Megakaryocytes

Question 21

Megakaryocytes have _____ nuclei

Answer 21

Many (multinucleate)

Question 22

Describe how platelets are made

Answer 22

Megakaryocyte produces pseudopods that are anuclear fragments. However these are very active, with receptors and intracellular signaling molecules. These pseudopods become platelets.

Question 23

EPO is constitutively produced in the _____ and inducible in the _____

Answer 23

Liver

Kidneys

Question 24

G-CSF is a glycoprotein that stimulates the bone marrow to produce granulocytes and release them into the bloodstream. Describe how the body goes about secreting G-CSF.

Answer 24

It is inducible in macrophages, fibroblasts, and endothelial cells by inflammatory signals

Question 25

* TPO (thrombopoeitin) is constitutively produced in the ______ and ______ and is inducible in the ______ and _____ by response to \_\_\_\_\_\_. * The major regulator of TPO production is \_\_\_\_\_

Answer 25

* Liver and kidneys * Liver and bone marrow, IL-6 * Platelet count

Question 26

c-MpI is a receptor on platelets that binds to TPO in the blood. How does [platelets] regulate their own production through this receptor interaction?

Answer 26

When TPO binds to c-MpI on platelet, then that TPO is destroyed by the platelet. As such, it does not travel to bone marrow and does not stimulate megakaryocyte to produce more platelets. So when there are plenty of platelets, they regulate their own production in this manner. When platelet count is low, then the TPO is able to travel to the marrow and activate megakaryocytes.

Question 27

What signaling molecule stimulates differentiation into a monocyte? Into a granulocyte?

Answer 27

M-CSF IL-5

Question 28

For lympoid tissues: * IL-2 induces formation of \_\_\_\_ * IL-4 induces formation of \_\_\_\_\_ * IL-15 induces formation of \_\_\_\_

Answer 28

* T-cells (2T Frutti --\>2T --\> T cells) * B-cells (Before --\> B4 --\> B cells) * NK-cells

Question 29

Differentiation of an HSC into CMP or CLP results in loss of \_\_\_\_\_\_\_\_\_\_

Answer 29

self-renewal

Question 30

Cells in the myeloid lineage of bone marrow can be subdivided into 3 categories: Graulocytic, erythroid, and megakaryotic cells. The most primitive cell that will ultimately become granulocytes is called a blast. Describe the process of maturation from a blast to a neutrophil, eosinophil, basophil.

Answer 30

The blast: * Decreases in cell size, * Decreases in cytoplasmic basophilia (meaning decrease in polyribosomes) * Increases in cytoplasmic granules * Increase in lobulation of the nucleus The granules that distinguish neutrophil, eosinophil and basophil become specific become specific about half way through this process. Bands are the last common cell to neutrophils, eosinophils and basophils.

Question 31

What does it indicate if a person has a lot of bands in their peripheral blood?

Answer 31

Bands are immature granulocytes, so a large number of them in the blood would indicate that the body is rapidly mobilizing cells of the innate immune system in an effort to fight off an infection.

Question 32

Describe the process of maturation of an erythroid.

Answer 32

Erythroblast --\> normoblast --\> reticulocyte --\> RBC As the cels progress through these phases they undergo: * Cells become less blue * Decreased cytoplasmic volume * Decreased nuclear size * Increased nuclear density * Loss of nucleus

Question 33

What is the difference between a reticulocyte and an erythrocyte?

Answer 33

Reticulocytes are the last progenitor cell of erythrocytes in the bone marrow. They are anucleate. During RBC maturation in the bone marrow, the cell would have synthesized all the Hb that it will need for its lifetime and acquired sufficient iron for its lifetime use. As the erythrocyte circulates it assembles Hb as needed for O₂ transport. Failure to acquire enough Iron during maturation leads to cell death and anemia.

Question 34

B cells mature in the \_\_\_\_\_\_ T cells mature in the \_\_\_\_\_\_

Answer 34

Bone marrow Thymus