[W2] WBCs- granulocytes Flashcards
what are polymorphonuclear WBCs called?
granulocytes
what are the 3 types of granulocytes?
- neutrophils
- eosinophils
- basophils
what are the 2 types of mononuclear WBCs?
- lymphocytes
- monocytes
what 2 WBCs are phagocytes?
- neutrophils
- monocytes
what do myeloid WBCs mature?
in the bone marrow
name 3 cytokines that are involved in the production of neutrophils
IL3
GM-CSF
G-CSF
what are IL3 cytokines produced by?
T cells
what are GM-CSF cytokines produced by?
T cells, endothelial cells,
monocytes, fibroblasts
what are G-CSF cytokines produced by?
Endothelial cells, placenta,
monocytes
name 3 cytokines that are involved in the production of eosinophils
IL3
IL5
GM-CSF
what are IL5 cytokines produced by?
T cells, basophils
name 3 cytokines that are involved in the production of basophils
IL3
IL4
GM-CSF
what are IL4 cytokines produced by?
B & T cells, eosinophils
what are the normal counts of neutrophils in the blood?
when are they elevated?
- 1.8-7.5 x10^9/L
- Bacterial infection, stress,
exercise, myeloproliferative
diseases e.g. leukaemia
what are the normal counts of lymphocytes in the blood?
when are they elevated?
- 1.5-4.0 x10^9/L
- Viral infection, lymphoproliferative diseases
(e.g. lymphocytic leukaemia)
what are the normal counts of monocytes in the blood?
when are they elevated?
- 0.2-0.8 x10^9/L
- Infection, inflammation, tissue damage, monocytic leukaemia
what are the normal counts of eosinophils in the blood?
when are they elevated?
- 0-0.4 x10^9/L
- Allergy, intestinal parasites,
hypereosinophilic syndrome,
eosinophilic leukaemia
what are the normal counts of basophils in the blood?
when are they elevated?
- 0.01-0.1 x10^9/L
- Some myeloproliferative
diseases (esp. Chronic
granulocytic leukaemia)
what is the main role of neutrophils?
the elimination of invading bacteria and some fungi
what is the main role of eosinophils?
elimination of parasitic worms
(=helminths), regulation of local immune and inflammatory responses
what is the main role of basophils?
Immune system regulation, secretion of heparin and histamine, allergy, inflammation, parasite defence, ? tumour surveillance
what is granulocyte nimenclature based on?
Nomenclature based on
staining with Romanowsky
stains (methanol fixation then
methylene blue + eosin)
what stains neutrophil granules?
granules are neutral-staining
what stains eosinophil granules?
granules stain with eosin (orange)
what stains basophil granules?
granules stain intensely with
methylene blue
what are the 6 stages to neutrophil maturation?
- blasts
- promyelocytes
- myelocytes
- metamyelocytes
- “band form” neutrophils
- neutrophils
what is the granulocyte turnover per day?
50 - 320 x10^9
How long do neutrophils typically spend in peripheral blood?
About 7 hours (circulating & marginal pools).
Where do neutrophils migrate after circulating in the blood?
Into tissues, likely in a random manner.
How long do neutrophils survive in tissues?
Around 20 hours before losing motility and undergoing apoptosis.
How are neutrophils removed after apoptosis?
They are cleared by monocytes/macrophages.
Where are many neutrophils lost in the body?
In the gastrointestinal (GI) tract.
How long do eosinophils circulate in the blood?
8–12 hours.
How long do eosinophils survive in tissues?
8–12 days.
Where are eosinophils commonly found in tissues?
Thymus, lower GI tract, ovary, uterus, spleen, and lymph nodes.
How long do basophils circulate in the blood?
2–3 days.
What happens to basophils after circulation?
They die
Why do neutrophils have a lobulated nucleus?
To aid deformability and motility.
How many lobes does a mature neutrophil nucleus typically have?
3–5 lobes.
What are the three types of neutrophil granules?
Primary, secondary, and tertiary granules.
What is the function of primary granules?
Discharge into phagosomes; contain microbicidal proteins (e.g., myeloperoxidase, hydrolases, lysozyme) for oxidative and non-oxidative killing of microorganisms.
What is the function of secondary granules?
Discharge into phagosomes and extracellularly; contain hydrolases, alkaline phosphatase, lysozyme, and collagenase.
What is the function of tertiary granules?
Contain alkaline phosphatase, gelatinase (collagen destruction), and cathepsin (a protease).
What is the primary function of neutrophils?
Destruction of invading bacteria and some fungi.
What are the two main processes involved in neutrophil function?
Chemotaxis and phagocytosis.
What is chemotaxis in neutrophils?
Movement up a concentration gradient to locate pathogens.
What are the two key steps in phagocytosis?
Engulfing and killing of microorganisms.
What is required for neutrophil chemotaxis?
Vessel wall adhesion and movement up a concentration gradient.
How do neutrophils adhere to the vessel wall?
Tissue damage triggers neutrophil adhesion to endothelial cells using adhesive membrane receptors.
Do neutrophils swim or crawl?
Neutrophils crawl, not swim.
How do neutrophils detect and move toward an infection site?
By following a concentration gradient of chemoattractants.
Name some chemoattractants that guide neutrophils.
Complement component C5a, bacterial metabolic by-products, leukotriene B4.
How sensitive are neutrophils to concentration changes?
They can detect changes as small as 2%.
What proteins are involved in neutrophil movement?
Myosin and actin, which enable contraction and movement.
What type of movement do neutrophils use?
Amoeboid movement via pseudopodia.
How do nanomolar levels of chemotactic attractants affect neutrophils?
They enable chemotaxis.
What happens at higher concentrations of chemotactic attractants?
They cause neutrophil degranulation.
Is the exact mechanism of neutrophil movement fully understood?
No, it remains unclear.
What is phagocytosis?
The process by which a phagocyte surrounds and destroys a foreign particle.
What is required for successful neutrophil phagocytosis?
Opsonization (coating) of the particle with IgG, IgM, or complement.
How does a neutrophil recognize and attach to a foreign particle?
Via receptors for opsonins.
What happens after the particle is ingested?
It is enclosed in a phagosome, which fuses with neutrophil granules to release antimicrobial contents.
What is the “respiratory burst” during phagocytosis?
A metabolic surge involving:
- Increased O₂ consumption
- Increased glycolysis
- Enhanced bactericidal processes (e.g., MPO activity)
- Increased expression of enzymes like alkaline phosphatase
How long does microbial killing in the phagosome usually take?
Around 20 minutes.
What are the two modes of microbial killing in the phagosome?
O₂-dependent killing:
- Myeloperoxidase (MPO) converts Cl⁻ + H₂O₂ into hypochlorous acid (HOCl), which is effective against bacteria, fungi, viruses, and tumor cells.
- H₂O₂ is generated by NADPH oxidase from O₂ via oxygen free radicals (O₂⁻).
O₂-independent killing:
- Uses enzymes like lysozyme.
What is an additional microbial killing mechanism used by neutrophils?
Neutrophil extracellular traps (NETs).
Do NETs require phagocytosis?
No, they are independent of phagocytosis.
What are NETs composed of?
Webs of DNA and proteases.
What is the function of NETs?
To trap and kill bacteria extracellularly.
How do NETs help in infection control?
They prevent the spread of infection.
What is myeloperoxidase (MPO) deficiency?
A common partial or total deficiency of MPO, with only 20% of patients being immunocompromised.
What compensates for MPO deficiency?
Oxygen free radicals (O₂⁻) and lysozyme.
What type of infection is most problematic in MPO deficiency?
Fungal infections.
What is respiratory burst failure, and which enzyme is affected?
A metabolic failure of microbial killing due to NADPH oxidase deficiency.
What inherited disease results from NADPH oxidase deficiency?
Chronic Granulomatous Disease (CGD).
Why does CGD cause persistent infections?
Some organisms survive inside the phagosome, leading to chronic infections and granuloma formation.
How does the body partially compensate for CGD?
Through non-oxidative killing mechanisms.
Are defects in neutrophil adhesion and migration common?
No, inherited defects are rare.
What are some acquired causes of neutrophil adhesion/migration defects?
Leukemia, diabetes, and renal failure, leading to varying susceptibility to sepsis.
How does neutrophil chemotactic activity in neonates compare to adults?
Neonate neutrophils have only 20–27% of the chemotactic activity of adults.
How does neutrophil function change in premature neonates?
It is even lower than in full-term neonates.
What happens to neutrophil function with age?
Chemotaxis and phagocytosis decline significantly in the elderly.
What are abnormal neutrophils in myelodysplasia called?
Hypogranular or agranular neutrophils.
In which conditions are abnormal neutrophils commonly found?
Myelodysplasia (“pre-leukemia”) and leukemia, especially in the elderly.
What is Chronic Granulocytic Leukaemia (CGL)?
Also known as Chronic Myelogenous Leukaemia, it is characterized by increased and unregulated growth of myeloid cells in the bone marrow.
What is the effect of CGL on myeloid cells in the blood?
There is an increase in myeloid cell numbers, with many early (but mostly differentiated) forms evident in the blood.
How are many cases of CGL now treated?
Many cases are “cured” with tyrosine kinase inhibitors like Imatinib.
What genetic mutation is commonly involved in CGL?
The 9:22 translocation, which deregulates tyrosine kinase activity.
What must be excluded before testing for primary neutrophil dysfunction?
Granulocytopenia (especially cyclic neutropenia) and defects in B cells or complement.
What percentage of primary immune deficiencies are caused by significant neutrophil dysfunction?
Less than 6%.
In which cases might neutrophil function testing be indicated?
- Chronic bacterial infections
- Increased susceptibility to bacterial infections
- Therapy-resistant infections
- Recurrent infections with nonpathogenic microorganisms
- Abscesses of the liver or lung
How is neutrophil function typically assessed in the lab?
Neutrophil function testing is rarely performed.
What is the Nitroblue tetrazolium (NBT) dye reduction test used for?
It is used for diagnosing Chronic Granulomatous Disease (CGD), assessing the neutrophil respiratory burst (production of active oxygen species like O₂⁻).
How does the NBT test work?
Active neutrophils reduce NBT to an insoluble blue compound, which is visualized under a microscope.
What has largely replaced the NBT dye reduction test?
Direct measurement of respiratory burst products using flow cytometry.
How is neutrophil motility tested?
By assessing the ability to penetrate a filter membrane or observing movement across a glass slide.
How is neutrophil phagocytosis tested?
- Ingestion: Observing the reduction in the number of free bacteria in a bacteria + neutrophil suspension.
- Killing: Observing the intra-cytoplasmic fall in the number of phagocytosed bacteria.
What method is increasingly replacing functional assays like motility and phagocytosis testing?
Flow cytometry.
Where are eosinophils normally found in the body?
In the thymus, lower GI tract, ovary, uterus, spleen, and lymph nodes.
They are not usually found in the lungs except in airborne allergies.
How do tissue eosinophil numbers compare to blood eosinophil numbers?
Tissue eosinophils are several hundred times more numerous than blood eosinophils.
What are the main functions of eosinophils?
- Key mediators of allergic inflammation
- Eliminate parasitic worm infections through antibody-dependent cell-mediated toxicity (IgE)
When are eosinophil numbers elevated?
In cases of allergy and helminth infections.
What is antibody-dependent cell-mediated toxicity (ADCC)?
ADCC is when an effector cell of the immune system lyses a target cell, whose membrane-surface antigens have been bound by specific antibodies (e.g., IgE for eosinophils).
Which antibody is involved in ADCC for eosinophils?
IgE (immunoglobulin E).
What is the function of eosinophil cationic protein?
It creates pores in the membranes of target cells, allowing the potential entry of other cytotoxic molecules and has anti-viral activity.
What is the function of Major Basic Protein?
It is toxic to parasites and epithelial cells, and causes the release of histamine and heparin from basophils and mast cells.
What are the properties of eosinophil-derived neurotoxin?
It has antiviral properties.
What is the role of eosinophil peroxidase?
It is active against microorganisms.
What is the result of eosinophil degranulation?
It causes significant local tissue damage.
What does IL-4 stand for, and what is its role in the immune system?
IL-4 stands for Interleukin-4, an important immunoregulatory cytokine. It affects inflammation, B-cell activation, and antibody production.
Do eosinophils produce IL-4?
Yes, eosinophils produce Interleukin-4 (IL-4).
How is Hypereosinophilic Syndrome defined?
It is defined as sustained unexplained eosinophilia greater than 1.5 x 10⁹/L for more than 6 months (normal range 0–0.4).
What type of population may be found in Hypereosinophilic Syndrome?
A monoclonal population of activated T lymphocytes, which produce excess IL-5.
What is the primary origin of the problem in Hypereosinophilic Syndrome?
The primary problem is lymphoid in origin, due to the excess production of IL-5 by activated T lymphocytes.
What causes organ dysfunction in Hypereosinophilic Syndrome?
Organ dysfunction is caused by eosinophilic infiltration of organs such as the heart, lungs, GI tract, spleen, skin, and CNS.
Are there cases of clonal Hypereosinophilic Syndrome?
Yes, some cases are clonal, also known as Eosinophilic leukaemia.
What is the nature of eosinophil growth in most cases of Hypereosinophilic Syndrome?
In most cases, eosinophils are independent of growth factor control, making it a myeloproliferative syndrome.
What treatments are used for Hypereosinophilic Syndrome?
Treatment aims to limit organ damage by controlling eosinophils using steroids, hydroxyurea, and chemotherapy (such as Imatinib).
What is the prognosis for Hypereosinophilic Syndrome?
Most cases are eventually fatal, but 80% of patients survive to five years. Early diagnosis and treatment are crucial.
What are the characteristics of basophils?
Rare, highly motile cells that die easily. Difficult to study.
How long do basophils mature and circulate?
Mature in the marrow for 2-7 days, circulate for 2-3 days, then die.
What was the original belief about basophils and mast cells?
They were thought to be identical, but now known to arise from different progenitor cells.
Where do basophils and mast cells mature?
Basophils mature in the marrow and circulate in the blood; mast cells mature in tissues.
What is the major growth factor for basophils and mast cells?
Basophils use IL-3; mast cells use Stem Cell Factor (SCF).
What substances do both basophils and mast cells contain?
Both contain heparin and histamine.
How do basophils and mast cells degranulate?
Basophils degranulate into internal phagosomes; mast cells discharge granules.
What is the role of basophils in the immune response?
They are key organizers of the local immune response.
Where do basophils accumulate during allergic reactions?
They accumulate at the site of allergic reactions, especially tick bites.
What activates basophils to release granule contents?
Basophils are activated by IgE, IL-3, C5a, GM-CSF, and insect venoms.
What do basophils release in response to activation?
They release granule contents, especially histamine.
What types of hypersensitivity reactions are basophils key mediators of?
Basophils are key mediators of immediate hypersensitivity reactions like asthma, urticaria, and anaphylaxis.
Can basophils suppress tumor cell growth?
Yes, basophils might suppress tumor cell growth.
What is the role of basophils in immunologic and inflammatory reactions?
Basophils orchestrate local immunologic and inflammatory reactions, especially those involving parasitic infections.
What are some substances secreted by basophils and their functions?
- Histamine: Chemotactic agent for eosinophils, vasodilator.
- Heparin: Anticoagulant.
- IL-3: Basophil growth factor, regulates macrophage and granulocyte populations in inflammation.
- IL-4: Attracts eosinophils, supports B-cell activation.
- IL-5: Promotes basophil and eosinophil production and activation, supports B-cell growth and activation.
What is the role of IL-13 secreted by basophils?
IL-13 promotes B-cell proliferation and differentiation.
What is the function of TNF-α secreted by basophils?
TNF-α is a pro-inflammatory cytokine.
What is the function of GM-CSF secreted by basophils?
GM-CSF is an inflammation-associated cytokine that activates neutrophils, moderates monocyte activation, and acts as a growth and differentiation factor for granulocytes and macrophages.
In which condition is significant basophilia common?
Significant basophilia is common in Chronic Myeloid Leukaemia.
Are basophilia and plasma triglyceride levels correlated?
No, any correlation is likely due to counting artefacts that give a falsely elevated basophil count.
In which other myeloproliferative disorders is basophilia found?
Basophilia is found to a lesser extent in myelofibrosis and Primary Proliferative Polycythaemia.
How common is basophil leukaemia?
Basophil leukaemia is very rare.
Why is treating basophil leukaemia difficult?
Treatment is difficult due to the release of histamine and other granule contents from basophils.
What is the Basophil Activation Test (BAT)?
BAT assesses the expression of activation markers (CD63 or CD203c) on the surface of live basophils or measures the degree of basophil degranulation.
How is the Basophil Activation Test performed?
It is performed on whole fresh blood by flow cytometry following stimulation with an allergen.
In which context is the Basophil Activation Test commonly used?
It is commonly used in the investigation of peanut allergy, using peanut allergen.
What does the Basophil Activation Test distinguish between?
It distinguishes between allergic and tolerant individuals.
How often is the Basophil Activation Test performed?
It is performed exceptionally rarely, with antigen challenges used instead.
What are mononuclear phagocytes called in peripheral blood?
In peripheral blood, mononuclear phagocytes are called monocytes.
What are mononuclear phagocytes called in tissues?
In tissues, mononuclear phagocytes are called macrophages.
Are monocytes and macrophages the same?
No, they are not quite the same, despite being part of the same phagocytic system.
What is the shape of the nucleus in monocytes?
Monocytes have a kidney-shaped nucleus.
What does the cytoplasm of monocytes look like?
The cytoplasm is abundant, grey-blue (“ground glass”) with fine reddish granules.
What enzymes are abundant in the cytoplasm of monocytes?
Monocytes contain many cytoplasmic enzymes, especially lysozyme, peroxidase, and esterases.
What do cytoplasmic vacuoles in monocytes indicate?
Cytoplasmic vacuoles are evidence of phagocytosis.
What kind of motility do monocytes exhibit?
Monocytes exhibit amoeboid motility and chemotaxis.
Where do monocytes accumulate in the body?
Monocytes accumulate at the site of inflammation.
Is it possible to visually differentiate some lymphocytes and monocytes?
No, it is impossible to visually differentiate some lymphocytes and monocytes.
What are the stages of maturation for monocytes and lymphocytes?
Both monocytes and lymphocytes mature as a blast → Pro (monocyte or lymphocyte) → mature form.
What is the precursor to monocytes in their maturation process?
Promonocytes are the precursor to monocytes.
What is the precursor to lymphocytes in their maturation process?
Prolymphocytes are the precursor to lymphocytes.
What is the common origin of monocytes and neutrophils?
Monocytes and neutrophils both originate from CFU-GM.
How long do blood monocytes survive, and where do they migrate?
Most blood monocytes die after about 24 hours, but some migrate into tissues like the spleen, lung, liver, and bone marrow after 1-3 days and develop into macrophages.
What is the ratio of monocytes to macrophages in the body?
The monocyte:macrophage ratio is about 1:400.
What is the role of macrophages in tissues?
Macrophages are self-replicating and play a role in phagocytosis and antigen presentation in tissues.
Who first used the term “macrophage” and why?
The term “macrophage” originated from Metchnikov’s work in 1882 to differentiate them from neutrophils (“microphages”) based on size.
When were monocytes named?
Monocytes were named later after staining techniques evolved to demonstrate nuclear detail.
What are the main functions of monocytes?
The main functions of monocytes include phagocytosis, antigen presentation to T cells, cytokine production, and differentiation into macrophages and monocyte-derived dendritic cells.
What role do monocytes play in immunity?
Monocytes have a critical role in both innate and adaptive immunity.
What adhesive glycoproteins do monocytes produce?
Monocytes produce various adhesive glycoproteins that facilitate their adhesion and chemotaxis to surfaces like endothelial cells.
What cytokines do monocytes release?
Monocytes release pro-inflammatory cytokines such as IL-1, IL-6, IL-8, G-CSF, and TNF-α.
What is the role of TNF-α in monocytes?
TNF-α is involved in cell signaling, apoptosis, and tumor cell suppression.
How do monocytes act as antigen-presenting cells?
Monocytes process phagocytosed pathogens and present their antigens to helper T cells via MHC Class II on the monocyte surface.
What types of particles can monocytes phagocytose?
Monocytes can phagocytose both opsonized and non-opsonized particles.
How long do most monocytes in circulation live?
Most monocytes in circulation are short-lived, surviving for about 24 hours.
How long do macrophages and dendritic cells live?
Macrophages and dendritic cells can live for months or years.
What is monocytosis, and when does it occur?
Monocytosis is an increased number of monocytes, which occurs in chronic infections and inflammatory conditions like tuberculosis and Crohn’s disease.
What is monocytic leukaemia?
Monocytic leukaemia can be either acute or chronic.
What are lipid storage diseases, and how do they affect monocytes?
Lipid storage diseases, such as Gaucher’s disease and Niemann-Pick disease, involve inherited impairment of phagocytosed material degradation, leading to the accumulation of debris within macrophages.
What are the effects of lipid storage diseases on the body?
Lipid storage diseases cause permanent cellular and tissue damage, particularly in the brain, peripheral nervous system, liver, spleen, and bone marrow.
