Haematology III Flashcards
What are the different types of white blood cells?
- Leukocytes
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinphils
- Basophils
What is the buffy coat?
the layer that exists between the blood cells in the bottom of a test tube and the plasma at the top. It is a thin layer that consists of the platelets and white blood cells
Why is there a larger buff layer in leukaemia?
due to increased WBCs
Give features of haematopoiesis for WBCs
- Lymphocytes derived from common lymphoid progenitor
- Rest of the white blood cells derive from common myeloid progenitor. Myeloid progenitor produces myeloblast which differentiates into either a basophil, neutrophil, eosinophil or monocyte
What are white blood cells also known as?
Leukocytes
What is a common physical characteristic across all white blood cells?
They are all nucleated
What are the roles of WBCs?
- Defence vs pathogens
- Toxins and waste removal
- Remove damaged cells
Where do WBCs mainly act?
outside tissues – in transit between sites of activity
What are the characteristics of WBCs?
- All can migrate out of the bloodstream. When WBCs in the bloodstream are activated they contact and adhere to the vessel walls in a process called margination. After further interaction with endothelial cells the activated SBCs squeeze between adjacent endothelial cells and enter the surrounding tissue. This process is called emigration or diapedesis
- All are capable amoeboid movement (most common mode of locomotion in eukaryotic cells – almost like a crawling movement)
- Neutrophils, eosinophils and monocytes are capable of phagocytosis
- All are attracted to specific chemical stimuli (when something is injured it releases chemicals and the leukocytes travel there)
What is the normal WBC count?
Approximately 4-11 x 10^9/litre blood
How are WBCs categorised and what is a good way of remembering this?
- characterised into granulocytes and agranulocytes
- those that end in ‘phil’ are granulocytes and those that end in ‘cyte’ are agranulocytes
What are the granulocytes?
- Neutrophils
- Eosinophils
- Basophils
What are the agranulocytes?
- lymphocytes
- monocytes
What is the RBC: platelet: WBC ratio in normal blood?
700:40:1
How much of the WBC count do neutrophils take up?
50-70% - most abundant
What is the structure of neutrophils?
- 9-15um diameter
- Distinctive nucleus, 2-5 lobes, granular cytoplasm
- Stain cytoplasm purple
- Variability in nuclear lobe
What is the function of neutrophils?
- First line of defence against bacterial infection
- Phagocytic
- Very Mobile
- Circulate in blood for approx. 10 hours
- only survive 30 minutes after performing phagocytosis
- Major constituent of pus (once dead)
- Also produces highly reactive, destructive chemical agents including hydrogen peroxide and superoxide anions which can kill bacteria
How much of the WBC count do eosinophils take up?
2-4%
What is the structure of Eosinophils?
- 10-12um in diameter
- Bilobular nucleus
What’s the function of eosinophils?
- Circulate in blood approximately 8-12 hours migrate to tissues
- Survive approximately 1-3 days
- Release toxic compounds, e.g. NO and cytoxic enzymes
- Allergies, asthma (increased number of eosinophils are an indicator of them)
- Combat parasitic infections
- Also attack bacteria, protozoa, debris
How much of the WBC count do basophils make up?
- > 1% - least abundant
What is the structure of Basophils?
- 8-10um diameter
- Bilobed ‘S’ shaped nucleus, large cytoplasmic granules
- Granules – histamine, heparin
What is the function of basophils?
- Inflammatory response
- Lifespan unknown
- Maybe precursors to mast cells – share a common bone marrow precursor
How much of the WBC count do monocytes make up?
2-10%
What is the structure of Monocytes?
- Largest WBC
- Up to 20um diameter
- Large kidney/horse shoe shaped nucleus often irregular
- Extensive cytoplasm
What is the function of monocytes?
- Little function in blood
- Migrate out of circulation after 3-4 days
- Turn into macrophages and reside in the tissue (survive here for months or years)
- Phagocytic
How much of the WBC count do lymphocytes make up?
20-30%
What is the structure of lymphocytes?
- Smallest WBC
- 6-15um diameter
- Lifespan: weeks to several years
- Regular nucleus with slight cytoplasm around it
What is the function of lymphocytes?
central role in all immunological defence mechanisms
How do lymphocytes circulate?
Circulate between various lymphoid tissues and all other tissues of body via blood and lymphatic vessels
What are the different types of lymphocytes?
- T cells: mediate cell-mediated immunity (e.g. transplant rejection)
- B cells: differentiate into plasma cells; secrete antibodies (humoral immunity)
- Natural Killer cells: ‘immune surveillance’ – important in preventing cancer
What is lymphocytosis?
increased lymphocyte count. This could be due to a viral infection or leukaemia
Where are most of the WBCs in the body at any moment?
In connective tissue proper of in organs of the lymphatic system
What leukocytes are part of the body’s non specific defence system?
- neutrophils
- eosinophils
- basophils
- monocytes
What leukocyte is part of the body’s specific immune response?
Lymphocytes
What is degranulation?
In a neutrophil the vesicle containing the engulfed pathogen will fuse with lysosomes that contain digestive enzymes and small peptides called defensins. This process is called degranulation because it reduced the number of granules in the cytoplasm
What do neutrophils release while actively attacking a bacteria?
prostaglandins and leukotrienes
What do prostaglandins do?
Increase capillary permeability in the affected regions contributing to local inflammation and restricting the spread of injury and infection
What do leukotrienes do?
Leukotrienes are hormones that attract other phagocytes and help coordinate the immune response
What else are eosinophils called?
acidophils
How do basophils increase the local inflammation initiated by mast cells?
Basophils migrate to injury sites and cross the capillary endothelium to accumulate in the damaged tissues. There they discharge their granules into the interstitial fluids. These granules contain histamine which dilates blood vessels and heparin a compound that prevents blood clotting. Stimulated basophils release these chemicals into the interstitial fluids to enhance the local inflammation initiated by mast cells
Give features of macrophages
- aggressive phagocytes
- When active they release chemicals that attract and stimulate neutrophils, monocytes and other phagocytic cells
- active macrophages also secrete substances that draw fibroblasts into the region
What is humoral immunity?
- immunity that produces antibodies
What do leukopenia and leucocytosis refer to?
- leukopenia indicates an inadequate number of WBCs
- Leucocytosis refers to excessive numbers of WBCs
What is the production of WBCs called?
leukopoiesis
What happens with the development of granulocytes?
Granulocytes complete their development in the red bone marrow. These WBCs proceed from blast cells to myelocytes to band cells before becoming mature WBCs
What happens with the development of monocytes?
Monocytes begin to differentiate in the red bone marrow. Then they enter the bloodstream and complete development when they become free macrophages in the peripheral tissues
What is lymphocytopoiesis?
the process of lymphocyte production
What do lymphocytes that are derived from lymphoid stem cells that remain in the red bone marrow differentiate into?
either B cells or natural killer cells
Where else are lymphocytes produced
In organs such as the thymus, spleen and lymph nodes
What do lymphoid stem cells migrating to the thymus mature into?
T cells
What colony-stimulating factors (CSFs) are involved in regulating WBC populations?
- Multi-CSF accelerates the production of granulocytes, monocytes, platelets and RBCs
- GM-CSF stimulates the production of both granulocytes and monocytes
- G-CSF stimulates the production of granulocytes
- M-CSF stimulates the production of monocytes
