Bone Marrow & Leucocytes

Question 1

Outline the development of white blood cells

Answer 1

Haemopoietic stem cells within the bone marrow differentiate into common myeloid progenitors or common lymphoid progenitors

Question 2

What are the Lymphoid Myeloid Progenitor cells?

Answer 2

Natural Killer Cells
B lymphocytes
T Lymphocytes
Immature Dendritic Cells

Question 3

What are the Common Myeloid Progenitor cells?

Answer 3

Megakaryocytes
Erythrocytes
Neutrophils
Basophils
Eosinophils
Macrophages
Dendritic Cells
Mast Cells

Question 4

Define the term Leucocytosis

Answer 4

High WBC count

Term can be interchanged with -philla

Question 5

Describe the typical features of Megakaryocytes

Answer 5

Present in bone marrow not normally blood

Rupture releasing thrombocytes (platelets) into circulation (clotting)

Question 6

Describe the typical features of Erythrocytes

Answer 6

Matured erythroblasts which have entered circulation

Red Blood Cells

Question 7

Describe the typical features of Neutrophils

Answer 7

Very fine, pale lilac granules

2-5 Lobed Nucleus

Most abundant WBC

10 – 12 microns in size

Development is influenced by GM-CSF

Derived from the same stem cell as macrophages

Question 8

What are the roles of neutrophils?

Answer 8

Circulate in the blood for minutes up to 6-8 hrs.

Survive in tissues 1 – 2 days

Neutrophils respond rapidly by chemotaxis to bacterial damage.

They then phagocytise pathogens and release lysozymes, strong oxidants and defensins to help fight the infection.

Performs both oxygen dependent & independent killing

Question 9

Outline the role of neutrophils in inflammation

Answer 9

Selectin receptors that interact with selectins on the endothelial cells

The interaction between selectins and their receptors slows the cells passage

Eventually neutrophils escape the blood vessel and gain access to the site of inflammation

Most abscesses dying neutrophils make up the majority of the pus

Question 10

Explain the process of neutrophils using oxygen dependent killing of phagosomes

Answer 10

Killing after phagocytosis ‘Respiritory burst’

Generate reactive oxygen species

Produce of hyperchloric acid

Question 11

Explain the process of neutrophils using oxygen independent killing of phagosomes

Answer 11

Killing in sites of poor blood flow or at abscesses

Lysosomes hydrolase the glycopeptide coats of the bacteria

Question 12

What is Left Shift?

Answer 12

Begin to see immature neutrophils due to stress

Often occurs during infection – acute phase

Circulating neutrophil numbers increase

Begin to see immature neutrophils or ‘band forms’ within the blood – leaving the BM early

Question 13

Outline the stages of neutrophil development in bone marrow

Answer 13

Myeloblast
Promyelocyte
Myelocyte
Metamyelocyte
Band Neutrophil - release prematurely if body is under mechanical stress
Segmented Neutrophils (matured)

Question 14

What are Heterophils?

Answer 14

Rabbit, reptiles, avian equivalent to ‘neutrophils

Functionally equivalent but granules stain RED

Question 15

Describe the typical features of Basophils

Answer 15

Large blue-black round granules in the cytoplasm that block the bilobed nucleus

Least common WBC (very rare to see)

Surface IgE Receptors

Rabbits > Ruminants & Horses >Cats & Dogs

Basophilia is the sign of pathology/disease

Question 16

Outline the role of Basophils

Answer 16

Exit capillaries and enter tissue fluids where they release heparin, histamine and serotonin during hypersensitivity (allergic) reactions to stimulate inflammation.

Question 17

Describe the typical features of Eosinophils

Answer 17

Red/orange, large uniform granules

2 but may have 3 connected nuclear lobes that tend to be more rounded and uniform

Question 18

What id the role of Eosinophils?

Answer 18

Combat histamine in allergic responses, phagocytize antigen-antibody complexes and destroy some parasitic worms.

Question 19

Describe the species differences with Eosinophils

Answer 19

Canine have intermediate sized granules

Felines have smaller & finer granules

equine & Bovine have larger round granules

Question 20

What is Equine idiopathic focal eosinophilic enteritis & diffuse eosinophilic enteritis?

Answer 20

Intestinal eosinophil inflammation
Unknown cause & linked to surgical colic cases

Question 21

What is Eosinophilic Granuloma Complex?

Answer 21

Skin condition of cats
Underlying allergy
Resulting in swelling, lesions, plaques
Collagen released by cells contributes to swelling

Question 22

What are Monocytes?

Answer 22

Arise from same precursors as neutrophils

Monocytes present within blood but not tissue
Reptiles have additional mononuclear cell - “azurophil”

Exit of blood into tissue or lymph node gives rise to macrophages and dendritic cells

Question 23

Describe the typical features of Macrophages

Answer 23

Monocytes that have differentiated in connective tissue

The cytoplasm appears to be “foamy” (because of numerous secondary lysosomes).

Oval or indented nucleus

Question 24

Outline the function of Macrophages

Answer 24

Phagocytosis pathogens, foreign bodies, antigen

Communicate with T-cells

Dendritic Cells

Question 25

Describe the typical features of Dendritic Cells

Answer 25

Peripheral antigen presenting cells which provide a connection between innate & adaptive immune response

Question 26

Describe the typical features of Mast cells

Answer 26

Connective tissue not blood Rounded nuclei Granular cytoplasm

Question 27

What is the function of Mast Cells?

Answer 27

Contain granules and histamine which promote inflammatory reaction when secreted Release of histamine causes endothelial cells lining venules to contract, weakening the junctions between these cells, and allowing proteins and cells from the plasma to leak through into the connective tissue. These cell play a key role in allergic reactions. Histamine also causes constriction of the bronchioles, and vasodilatation

Question 28

Describe the typical features of Natural Killer Cells

Answer 28

Large granular lymphocytes Participate in early cytotoxic responses against viruses, parasites, microbial pathogens, as well as tumour immunosurveillance

Question 29

Describe the typical features of B Lymphocytes

Answer 29

Arise and mature in Bone Marrow (or bursa of Fabricius in birds) Vary in size with small lymphocytes being 6-9 µm and large lymphocytes 10-14 µm in diameter. Nucleus stains dark and is round or slightly indented with the cytoplasm appearing as a rim around the nucleus.

Question 30

Describe the typical features of T Lymphocytes

Answer 30

Develope in bone marrow and then move to Thymus Vary in size with small lymphocytes being 6-9 µm and large lymphocytes 10-14 µm in diameter. Nucleus stains dark and is round or slightly indented with the cytoplasm appearing as a rim around the nucleus.

Question 31

What is the Diff Quick stain?

Answer 31

Most common stain using Eosin and Azure dye Creates Romanowsky stain effect - mixing of two stains Eosins stains basic tissue components orange (to pink). These components are know as eosinophilic or acidophilic Azure stains acidic tissue blue (to black). These components are known as basophilic

Question 32

What is the Leishman stain?

Answer 32

Used on blood smears Can also distinguish certain protozoan parasites

Question 33

What is the Wright stain?

Answer 33

Used on BM aspirates & blood smears

Question 34

What is the Giemsa Stain?

Answer 34

Staining cytoplasm shades of pink Used on blood smears

Question 35

How would you perform a differential cell count?

Answer 35

Obtain an accurate total WBC count by machine or manual haemocytometer. Cells x 109/L Manual required for birds, reptiles species with nucleated red cells). Use blood smear to count and classify 100 or 200 WBC cells calculate an absolute number for each type (109/L) from % and total WBCC Or use blood smear to check differential output from machine

Question 36

What is bone aspirate used for?

Answer 36

Cytopathologists review BM for the following: Presence of RBC precursors Presence of WBCC precursors Presence of megakaryocyte Myeloid: Erythroid (M:E) ratio Orderly progression of cells through precursor stages and presence of final mature stages.