Bone Marrow & Leucocytes Flashcards
Outline the development of white blood cells
Haemopoietic stem cells within the bone marrow differentiate into common myeloid progenitors or common lymphoid progenitors
What are the Lymphoid Myeloid Progenitor cells?
Natural Killer Cells
B lymphocytes
T Lymphocytes
Immature Dendritic Cells
What are the Common Myeloid Progenitor cells?
Megakaryocytes
Erythrocytes
Neutrophils
Basophils
Eosinophils
Macrophages
Dendritic Cells
Mast Cells
Define the term Leucocytosis
High WBC count
Term can be interchanged with -philla
Describe the typical features of Megakaryocytes
Present in bone marrow not normally blood
Rupture releasing thrombocytes (platelets) into circulation (clotting)
Describe the typical features of Erythrocytes
Matured erythroblasts which have entered circulation
Red Blood Cells
Describe the typical features of Neutrophils
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
What are the roles of neutrophils?
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
Outline the role of neutrophils in inflammation
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
Explain the process of neutrophils using oxygen dependent killing of phagosomes
Killing after phagocytosis ‘Respiritory burst’
Generate reactive oxygen species
Produce of hyperchloric acid
Explain the process of neutrophils using oxygen independent killing of phagosomes
Killing in sites of poor blood flow or at abscesses
Lysosomes hydrolase the glycopeptide coats of the bacteria
What is Left Shift?
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
Outline the stages of neutrophil development in bone marrow
Myeloblast
Promyelocyte
Myelocyte
Metamyelocyte
Band Neutrophil - release prematurely if body is under mechanical stress
Segmented Neutrophils (matured)
What are Heterophils?
Rabbit, reptiles, avian equivalent to ‘neutrophils
Functionally equivalent but granules stain RED
Describe the typical features of Basophils
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
Outline the role of Basophils
Exit capillaries and enter tissue fluids where they release heparin, histamine and serotonin during hypersensitivity (allergic) reactions to stimulate inflammation.
Describe the typical features of Eosinophils
Red/orange, large uniform granules
2 but may have 3 connected nuclear lobes that tend to be more rounded and uniform
What id the role of Eosinophils?
Combat histamine in allergic responses, phagocytize antigen-antibody complexes and destroy some parasitic worms.
Describe the species differences with Eosinophils
Canine have intermediate sized granules
Felines have smaller & finer granules
equine & Bovine have larger round granules
What is Equine idiopathic focal eosinophilic enteritis & diffuse eosinophilic enteritis?
Intestinal eosinophil inflammation
Unknown cause & linked to surgical colic cases
What is Eosinophilic Granuloma Complex?
Skin condition of cats
Underlying allergy
Resulting in swelling, lesions, plaques
Collagen released by cells contributes to swelling
What are Monocytes?
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
Describe the typical features of Macrophages
Monocytes that have differentiated in connective tissue
The cytoplasm appears to be “foamy” (because of numerous secondary lysosomes).
Oval or indented nucleus
Outline the function of Macrophages
Phagocytosis pathogens, foreign bodies, antigen
Communicate with T-cells
Dendritic Cells
Describe the typical features of Dendritic Cells
Peripheral antigen presenting cells which provide a connection between innate & adaptive immune response
Describe the typical features of Mast cells
Connective tissue not blood
Rounded nuclei
Granular cytoplasm
What is the function of Mast Cells?
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
Describe the typical features of Natural Killer Cells
Large granular lymphocytes
Participate in early cytotoxic responses against viruses, parasites, microbial pathogens, as well as tumour immunosurveillance
Describe the typical features of B Lymphocytes
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.
Describe the typical features of T Lymphocytes
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.
What is the Diff Quick stain?
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
What is the Leishman stain?
Used on blood smears
Can also distinguish certain protozoan parasites
What is the Wright stain?
Used on BM aspirates & blood smears
What is the Giemsa Stain?
Staining cytoplasm shades of pink
Used on blood smears
How would you perform a differential cell count?
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
What is bone aspirate used for?
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.
