Leukocytes Flashcards
These are colorless nucleated cells that circulate in the peripheral blood that seve as main line of defense against foreign antigens and are also called as white blood cells
Leukocytes
*found in bone marrow, peripheral blood, tissues
Leukocytes for antibody production and other activities of the immune response
immunocytes
lymphocytes
leukocytes which engulf and destroy
phagocytes
Neutrophils, eosinophils, basophils, monocytes
two major lineages of leukoycte formation
→ Myeloid: RBCs, platelets, granulocytes, monocytes
→ Lymphoid: Lymphocytes, NK cells
These are formed in the red bone marrow
Granulocytes, monocytes and few lymphocytes
These are formed in the lymph tissues
lymphocytes and plasma cells
formation of granulocytes within the bone marrow
Granulopoiesis
*Life span after release
→ 4-8 hours in blood
→ 4-5 days in tissues
What inhibits granulopoiesis?
→ Inhibited (negative feedback) by mature granulocytes and
the bone marrow microenvironment
When is granulopoiesis increased?
→ Increase ten-fold in patients with sustained infections or other inflammatory conditions
Genesis of lymphocytes
→ Lymphoblasts become T and B lymphocytes
→ Continuously enter blood and drain from lymphatic systems
→ In a few hours, goes back to tissues by diapedesis
→ Life span: weeks to months
What are the routine methods for identifying types of leukocytes?
→ Peripheral blood smear
→ Wright’s stain
[granulocytes in wright stain] basic; pink and reacts with eosin (-) which is an acidic dye
Eosinophils
[granulocytes in wright stain] Basophil reaction
acidic; purple-blue; reacts with methylene blue (+) which is a basic dye
[granulocytes in wright stain] neutrophil reaction
neutral; light pinkish purple or pink-tan
granulocytes and non-granulocytes
Granulocytes (also polymorphonuclear) Neutrophil 62% Eosinophils 2.3% Basophils 0.4% Non-granulocytes (also mononuclear) Monocyte 5.3% Lymphocyte 30% (plasma cells)
Criteria for identifying leukocytes
• Cell size • Nucleus-cytoplasm ratio (N/C) → High ratio: nucleus occupies most cell area with only small rim of cytoplasm → Low ratio: nucleus small in relation to volume of cytoplasm • Cytoplasm characteristics → Color of background → Presence or absence of granules → Color and size of granules • Nuclear characteristics → Shape → Color → Chromatin pattern → Presence or absence of nucleoli
a high ratio of nucleus-cytoplasm indicates
nucleus occupies most cell area with only small
rim of cytoplasm
size of neutrophils
uniform, 12-15 micrometers
nucleus with 2-5 lobes joined by solid filament
movement of neutrophils
amoeboid motion using pseudopodium (phagocytic)
life span of neutrophils
9-10 days (depends on passing from BM to PB into tissues)
- BM-mitotic: 2-3 days; maturation and storage: 5-7 days
- PB: 7 hours (circulating and marginal neutrophil pools)
- tissues:2-3 days
mitotic “neutrophils” in bone marrow
myeloblasts, promyelocytes and myelocytes
[neutrophils] maturation and storage at bone marrow
metamyelocytes, bands and segmented
Maturation of neutrophils
Myeloblast, Promyelocyte,
Myelocyte, Metamyelocyte, Band Cell, Neutrophil Granulocyte
factor driving neutrophil maturation
G-CSF
characterizes maturation
→ Decreasing N/C ratio
→ Increasing granule production and nuclear segmentation
These precursors are confined to the bone marrow and with basophilic cytoplasm
Myeloblast (scant basophilic c.; in patients with myeloid leukemia, numerous myeloblasts)
Promyeloblast (bc with multiple azurophilic granules)
Myelocyte (abundant pink cytoplasm with azurophilic and specific ganules)
[Precursor cells of neutrophils]
most immature large cells and comprise 3% of nucleated cells (15-20 micrometers with 7-5:1 N/C ratio)
Myeloblast
- may contain auer rods
- round nuclei with clefts (one or more nucleoli)
[Precursor cells of neutrophils]
These are seen in blood in pathologic states
Promyeloblast (<2%)*
Myelocyte (10%)
Metamyelocyte (15-20%)- in response to stress
Band cell??
*with fine chromatin and distinct nucleoli
[Precursor cells of neutrophils] smaller cells (10-18 micrometers) with slightly indented nucleus, no nucleolus, with chromatin clumping
Myelocyte
[Precursor cells of neutrophils] Nucleus is indented, lacks nucleolus, with condensed chromatin with rare azurophilic or pink (primary) and many specific (secondary) granules are present
Metamyelocyte
[Precursor cells of neutrophils] comprise 1-3% of peripheral wbcs, smaller, 10-15 micrometers with many shaped nucleus and twisted/folded on itself (sausage/s/u like) with condensed nuclear chromatin with abundant pink cytoplasm with neutrophilic specific granules with few azurophilic granules
Band cell
*numerous = losing battle
→ Predominant white blood cell → 10 to 15 micrometers in diameter → N:C ratio= 1:3 → Nucleus is segmented or lobulated (2 to 5 lobes) § Connected by a thin filament § Condensed nuclear chromatin § Pale cytoplasm with specific granules
Segmented Neutrophils
Function of neutrophils
- It mediates immune response against infectious agents.
* It has granules which aid in killing bacteria
neutrophil granules which are smaller electron lucent and contain lactoferrin and lysozyme wc are formed in myelocytes
Secondary/specific granules
neutrophil granules with gelatinase and alkaline phosphatases
Tertiary
large, round, red-pink neutrophil granules which are formed in promyelocyte
Primary/Azurophilic
These are found in primary granules
myeloperoxidase (can kill), elastase, lysozyme, cathepsin G, acid hydrolases
neutrophil granules wc are considered as secretory vesicles
quaternary
Mechanism of attacking and destroying bacteria by neutrophils
→ Enter the tissue spaces by diapedesis
→ Move through tissue spaces by amoeboid motion
→ Attracted to inflamed areas by chemotaxis
→ Engulf offending agent through phagocytosis
→ Granules discharge their contents (Hydrogen peroxide superoxide) into vacuole to digest
These are <1% of WBCs which are characterized by its ability to be stained by basic dyes (purple- black)
basophils
- 10-15 micrometers
- band/lobed nucleus
When are basophils increased in blood?
during myeloproliferative neoplasms, hypersensitivity reactions, hypothyroidism, iron deficiency and renal disease
When are basophil progenitor cells increased?
atopic persons
*same maturation as neutrophils but nucleus does not segment
These are factors which play a key role in basophil production
→ IL3 (main cytokine)
→ GM-CSF, IL4, IL5, stem cell factor
Functions of basophils
- Mediates allergic or hypersensitivity reactions
- Granules contain histamine, mucopolysaccharides, peroxidase, chymase, tryptase, Charcot-Leyden crystal protein, PAF, and ECF-A
- Some phagocytic activity
- Role in host defense against helminths
How do basophils mediate allergic or hypersensitivity reactions?
→ Liberate heparin (anticoagulant), histamine, bradykinin, serotonin and leukotrienes
→ Role in immediate hypersensitivity reactions (w/ specific receptors for IgE)
→ Role in delayed type hypersensitivity reactions (T cells activate basophils to release histamine)
These are 1-4% of all WBCs whose granules stain deeply with orange-red eosin who survive longer in tissues than neutrophils found mostly in skin and mucosal surfaces of RT and GIT
Eosinophils
- 10-15 micrometers with NC ratio 1:3 and 2 or more lobed nucleus connected by thin filament
- same neutrophil maturation
common progenitor of eosinophil, neutrophil and basophil
CFU-GM
This induces eosinophil formation, enhances function and prolonged survival
IL5 growth factor
*other factors: IL1, IL3, IL9
differentiate immature vs mature eosinophils
- Immature: large blue granules
* Mature: refractive orange specific granules
[Precursors of the Mature Eosinophil]
• immature or juvenile
• Horseshoe shaped nucleus
Eosinophilic band
[Precursors of the Mature Eosinophil]
→ No cell division
→ Indented nucleus
→ Acidophilic granules
Eosinophilic metamyelocyte
[Precursors of the Mature Eosinophil]
→ Primary and secondary granules
→ Round nucleus with coarse chromatin
Eosinophilic myelocyte
[Precursors of the Mature Eosinophil]
→ Mature
→ Lobulated nucleus with chromatin thread
Eosinophil segmented
functions of eosinophils
• Role in response to parasitic infections and allergic conditions
• Phagocytosis
• Respond to chemotactic factors
→ In immediate hypersensitivity, eosinophils drawn by
basophils and mast cells
• Immunomodulation of hypersensitivity reactions
→ Histaminases and arylsulfatase for the breakdown of enzymes
• Destruction of parasitic helminthes
→ Major basic protein function as a cytotoxin
These comprise <1% of bone marrow cells, 0-10% in PB; largest of all leukocytes N:C=65-80%
Monocytes
*round with smooth margins or pseudopod-like cytoplasmic extensions with abundant light-blue cytoplasm with fine pink azurophilic granules
Nucleus of monocytes
Large, bilobed, kidney shaped or U shaped nucleus with moderately clumped chromatin
*no nucleolus
Life span of monocytes
→ In BM - same progenitor cell with neutrophils • Promonocyte first recognizable cell • 30 – 48 hours → In peripheral blood • 70 hours → In tissues • Differentiate into macrophages • Remain for several months
monocytes are precursors of
most macrophages and dendritic cells
Precursor cells of moncytes
Monoblast
Promonocyte
[Precursor cells of moncytes] → Actively dividing → More irregular nuclear contour → Less basophilic cytoplasm § Gray-blue cytoplasm with uniformly distributed azurophilic granules → Indented or lobulated nucleus
Promonocyte
[Precursor cells of moncytes]
→ 12 – 20 microns
→ Moderate basophilic, agranular cytoplasm
→ May show pseudopod formation
→ Round / oval nuclei with fine chromatin and 1 – 4 large prominent nucleoli
§ May show indentations
→ N:C ratio: 4:1 to 3:1
Monoblast
Functions of monocytes
• Part of innate immune system (Replenish macrophages and dendritic cells)
• Produce numerous regulatory cytokines
• Phagocytosis
• Chemotactic factors that attract monocytes
(Ag-Ab complexes, complement components, factors released by activated T lymphocytes)
• Differentiates to macrophages
→ Greater killing potency
→ APCs
→ Release various substances for inflammatory response, complement system, and pyrogens
• Granules
Granules of lymphocytes contain
→ Variety of lysosomal enzymes • Acid phosphatase, β-glucoronidase, lysozyme, lipase, peroxidase • Nonspecific esterases → Lysozyme released continuously • Bacteriolytic enzyme • Enhance effect of phagocytosis • Potential antineoplastic effect
These non-obligate end cells are distributed 15-60% in peripheral blood
Lymphocytes
- heterogenous and pre-destined to migrate
- size: 7-9 microns to 10-18 microns N/C: 1.5:1
Nucleus characteristics of lymphocytes
→ Oval and slightly indented
→ Nuclear chromatin: markedly condensed
→ Nucleoli are absent and a definite nuclear membrane is present
cytoplasm characteristics of lymphocytes
→ Light blue to blue with a perinuclear clear zone around the nucleus
→ Few azurophilic granules
Where do lympocytes originate from?
bone marrow
[Maturation of lymphocytes] Where does terminal differentiation of mature lymphocytes occur?
secondary lymphoid organs
T or F: B:T cell ratio: proportion of B cells decreases as T cells
increases
true
→ Children: 2:1
→ 4 to 5 years old: 1:4-5
→ Adult levels are reached during adolescence
Precursor cells of lymphocytes
lymphoblast (N/C: 6:1)
prolymphocyte (N/C: 5:1)
*both 10-18 microns in diameter
[Precursor cells of lymphocytes] Round shape and stains reddish-purple nucleus with fine, well-distributed nuclear chromatin with one or more nucleoli present
lymphoblast
- Deep blue cytoplasm with a frequent perinuclear clear zone
[Precursor cells of lymphocytes] Oval and slightly indented nucleus with coarse and slightly clumped nuclear chromatin with one light blue nucleolus usually present
prolymphocyte
*Light blue to dark blue cytoplasm with few red-purple (azurophilic) granules
functions of lymphocytes
• Play a major role in the maintenance of health and disease
→ Humoral immune response: Mature B cells
→ Cell-Mediated immune response: T/ NK cells
• Antigen recognition and generation of appropriate immune response
→ T cells: regulatory and effector functions
→ B cells: differentiate into plasma cells
→ NK cells: recognize and lyse tumor and virus-infected cells
Provides relative percentage of each type of white blood cell and helps reveal abnormal WBC populations
WBC differential count
- Each differential adds up to 100%
- Specimen: Whole blood in EDTA
Advantages of absolute count over relative counts
→ Gives more meaningful information
→ Useful for monitoring
→ Abnormal conditions can be identified
Methods of WBC differential count
Automated differential (uses fluorescence flow cytometry and electrical impedance;1000s) Manual dbc (visual examination of peripheral blood smear by trained personnel;1000-2000)
What are difficult to identify in both methods of WBC differential count?
Band neutrophils and immature granulocytes
*also monocytes and basophil counts
Disadvantage of both methods
cannot identify small numbers of abnormal cells and most difficult in id lymphoma cells and reactive lymphocytes
→ Precision-made slide for performing manual cell counts with the aid of a microscope
Hemacytometers
When are hemacytometers used?
see WBC count tinatamad na ako
→ Automated cell counters and hematology analyzers are unavailable
→ Blood cell counts are extremely low
→ To get a cell count for body fluids(spinal fluid, joint fluid, semen counts, and other bodily fluids)
