Leukopoiesis

Question 1

Mast Cells vs. Basophils

Answer 1

Mast Cell: CT, occasionally divides, no cells in circulation, lives for weeks to months, 20-30um, round nucleus, many large granules

Basophils: bone marrow, does not divide, has cells in circulation, lives for a few days, 7-10um, segmented bipolar nucleus, few small basophilic granules

Both: IgE receptors, hemopoietic stem cells

Question 2

Mast Cell Products

Answer 2

Prostaglandin D2 = cyclooxygenase
Leukotriene C4 = lipoxygenase
Both are important inflammatory mediators when IgE elicits release

Question 3

Lineage of Granulocytes

Answer 3

Start in bone marrow with myeloblast, promyelocyte, myelocyte, metamyelocyte, then band cells (process for all three granulocytes)

Band cells: talk about neutrophils mostly, but also basophils and eosinophils

Question 4

Granule Formation and Mitosis of Granulocyte Lineage

Answer 4

Different lysosomes and specific granules forming to determine what type of cell it will develop into
Azurophilic granules: primary granules in promyelocyte stage ONLY; synthesized by rER and packed in Golgi
Myelocyte stage is the last stage mitotic division occurs in and is the first stage with specific granules
Metamyleocyte characterized by indented (deep or shallow depending on time) nucleus

Question 5

Myeloblast

Answer 5

Myeloblast: high nucleus: cytoplasm ratio, 3-5 nucleoli, prominent Golgi, and no granules

Question 6

Promyelocyte

Answer 6

Primary granules are also known as azurophilic granules. They are lysosomes that stain blue with azurophilic stains.
They are produced in this stage only. Thus, with subsequent mitoses, the number of azurophilic granules in the cytoplasm decreases.
More cytoplasm
Prominent Golgi

Question 7

Myelocyte

Answer 7

Eccentric ovoid nucleus
Specific granules appear (first stage)
Can still divide

Question 8

Metamyleocyte

Answer 8

Nucleus indented
Max density of granules
No longer mitotic

Question 9

Band Cells

Answer 9

Horseshoe nucleus;
Rarely seen in eosino & basophils
0 – 3% in circulation
The appearance of large numbers of immature neutrophils (band cells) in the blood is called a “shift to the left” and is clinically significant, usually indicating bacterial infection.

Question 10

Mononuclear Phagocytic System

Answer 10

Histiocytes (CT)
Osteoclasts (bone)
*Microglia (nervous tissue) - from neural crest cells
Dendritic cells (lymph nodes, spleen)
Langerhans cell (epidermis)
Dust cells (lung macrophages)
Kupffer cells (liver macrophages)
Sinusoidal lining cells (spleen)
Mesangial cells (kidney)

*All but microglia are made from monocytes

Question 11

Macrophages

Answer 11

APC - antigen presenting cells; phagocytose Ag and break down into peptides and put it on MHC (major histocompatibility complex) and present to T helper cells

Question 12

Monopoiesis

Answer 12

Development into monocyte takes ~55 hrs

Monocyte precursors in bone marrow:
Monoblast to promonocyte to monocyte

Monoblast: large cell with indented nucleus
Promonocyte: bit smaller and capable of division, but cannot after this stage; nucleus indented
Monocyte: C shaped nucleus
Monocyte progenitor cells then develops into macrophage once in the tissue

Question 13

Lymphocyte Development

Answer 13

Hemopoietic stem cells form into common lymphoid progenitor cells to form B cells, T cells (cytotoxic and helper), and NKC

Question 14

Lymphopoiesis

Answer 14

Several classes of lymphocytes
Helper T cells (~46%)
B cells 	  (~23%)	
Cytotoxic T cells (~19%)	
NK cells 	  (~7%)

Originate from stem cell in marrow:
Lymphoblast  prolymphocyte lymphocyte

T cells mature in thymus
B cells mature in bursa-equivalent organs (bone marrow, GALT, spleen)

Question 15

Lymphoblast vs. Prolymphocyte

Answer 15

Lymphoblast:
High nucleus:cytoplasm ratio
Strongly basophilic cytoplasm
1 – 2 nucleoli

Prolymphocyte:
More cytoplasm
Less basophilic cytoplasm
Nucleoli poorly visible
In blood sometimes