leucocytes
TRANSCRIPT
DR NILESH KATE
MBBS,MDASSOCIATE PROF
DEPT. OF PHYSIOLOGY
LEUCOCYTESWHITE BLOOD
CELLS.
OBJECTIVES. Types of WBC and their counts Formation of WBC Morphology, life span, functions and
variations in count of WBC Applied aspects.
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INTRODUCTION Crucial in the body’s defense against pathogens
These are complete cells, with a nucleus and organelles
They lack Hb so they are colorless (i.e. white)
Able to move into and out of blood vessels (Diapedesis)
Can respond to chemicals released by damaged tissues (Chemotaxis)
Some are capable of Phagocytosis
TYPES OF LEUKOCYTES Granulocytes
Granules in their cytoplasm can be stained
Biologically active substances involved in inflammatory and allergic reactions.
Neutrophils, Eosinophil, and Basophils
TYPES OF LEUKOCYTES Agranulocytes
Lack visible cytoplasmic granules
Lymphocytes and Monocytes
TYPES OF LEUKOCYTES
LEUKOCYTE LEVELS IN THE BLOOD
Normal levels =4,000 to 11,000 cells/mm3
Abnormal leukocyte levels
Leucocytosis
Above 11,000 leukocytes/ml
Generally indicates an infection
Leucopenia
Abnormally low leukocyte level
Commonly caused by certain drugs
Figure 19.11
WHITE BLOOD CELLS
CONCEPT OF POOL There are 3 different areas in our body where different
WBCs reside1. Marrow pool: 90% neutrophils2. Blood pool: 3% 3. Tissue pool: 7% Genesis of WBCs: Leucopoiesis
In bone marrow → PHSC (Pluripotential hemopoietic stem cells) differentiates → committed stem cells → CFU-GM
Granulocytes & monocytes are formed only in bone marrow lymphocytes & plasma cells are produced in various
lymphogenous tissues
GENESIS OF WBCS (LEUKOPOIESIS):
REGULATION OF LEUCOPOIESIS
Granulopenia or Dead granulocytes and monocytes
Release G-CSF
M-CSF
GM-CSF
Interleukins IL-1, IL-3
Stimulate
Bone Marrow
Normal counts inhibit increased formation
Granulocytes, Monocytes/Macrophages Prostaglandins: Monocytes, Lactoferrin Cytokines: glycoproteins formed by monocytes and T- lymphocytes :
NEUTROPHILS: Size:10-14 µm in diam. Nucleus:
1. Multilobed (1-6 lobes) therefore called polymorphnuclear leucocytes.
2. Young cell have single horse shoe shaped nucleus.
3. As the cells grow older nucleus becomes multilobed. Lobes are connected with one another by chromatin threads.
4. Arneth count: Cytoplasm: contains neutrally stained
granules average half-life in the circulation is 6 hours
NEUTROPHILS:4 types of granules are present
1. Primary/ Azurophilic granules: less in no. enzymes like
i. myeloperoxidase, (produces HOCl for killing bacteria).
ii. lysosomal granules containing acid hydrolases, which can digest bacteria, elastase, proteinase, α-1 antitrypsin
iii. Antimicrobial proteins like cathepsin-G, Defensins- α, β
iv. Tissue destruction during inflammation
2. Secondary /Specific/peroxidase negative granules: more numerous. Contain
i. Lactoferrin-antibacterial
ii. Gelatinase, lysozyme- microbicidal, Vit B12 binding protein &
iii. Components of enzyme system that produce free radicals like H2O2, which kills the microbes.
iv. Substances that facilitates chemotaxis.
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NEUTROPHILS:3. Tertiary granules: Gelatinase, alkaline phosphatase and cytochrome-b
4. Secretory Granules: secretory vesicles contain CD3, phospholipase and tyrosine kinase
Toxic granules: During severe infections toxic coarse granules are seen. Functions:1. Phagocytosis:2. Reaction of inflammation: release leukotrienes, prostaglandins,
thromboxanes
3. Febrile Response: They contain fever producing substance, endogenous pyrogen which is an important mediator of febrile response to bacterial pyrogens.
NEUTROPHILS: These enzymes act in a cooperative fashion with the O2 –, H2O2, and HOCl formed by the action of
the NADPH oxidase and myeloperoxidase to produce a killing zone
around the activated neutrophil.
PROCESS OF PHAGOCYTOSIS (CELL EATING)
Phagocytes engulf and kill microorganisms
Steps of Phagocytosis:
1. Margination
2. Emigration and Diapedesis
3. Chemotaxis
4. Recognition and attachment(Opsonization)
5. Engulfment and creation of phagosome
6. Fusion of phagosome with lysosome
7. Destruction and digestion
8. Residual body Exocytosis
NEUTROPHIL RECRUITMENT
Selectins/Addressins ß2 –Integrin / ICAM-1
flow rolling adhesion transmigration
inflammatorymediators
Tissue Injury(e.g. Bacterial infection)
chemoattractant(e.g. IL-8, C5a), leukotrienes
• phagocytosis• oxidant production• lysosomal granules
endothelium
OPSONIZATION AND PHAGOCYTOSIS IgG and C3b opsonin proteins Fc receptors for antibody Complement receptors: (e.g. C3b) Other
receptors for collectins (eg. mannose-binding protein)
G protein-mediated responses, increased motor activity of the cell, exocytosis, respiratory burst
OPSONIZATION
RESPIRATORY BURST: NADPH OXIDASE
NADPH oxidase activation
Superoxide anion: O2-
Hydrogen peroxide: H2O2
Hydroxyl radical: OH .
Hypochlorous acid: HOCl
Myeloperoxidase = MPO
O2 + e-
2O2- + 2H+
H2O2 + Fe2+
H2O2
O2-
H2O2 + O2
OH + OH- + Fe3+
HOCl + OH-MPO
REACTIVE OXYGEN REACTIVE OXYGEN METABOLITESMETABOLITES
VARIATION IN NEUTROPHIL COUNT:
Neutrophilia: ↑ in neutrophils>10000/mm3
A. Physiological 1)After Exercise,
2)After injection of epinephrine,
3)Pregnancy, menstruation, parturition & lactation,
4)Newborn,
5)After meals,
6)Mental or emotional stress
B. Pathological 1)Acute pyogenic (pus forming)
bacterial infections,
2) Acute Rheumatic fever, Gout
2)Following tissue destruction,
i) Burns
ii) After hemorrhage,
iii) myocardial infarction, iv) After surgery
v) poisoning by lead, mercury,
NEUTROPENIA: ↓ IN NEUTROPHILS:
< 2500/mm3 In children Typhoid, paratyphoid fever Viral infection Malaria Aplasia of bone marrow Bone marrow depression due to
Chloromycetin, cytotoxic drugs X-rays & radiations Chemical poisons like arsenic
Size:10-14 µm in diam. (2%) Nucleus:
1. Usually (85%) cells ‘bilobed’.
2. Lobes are connected with one another by chromatin threads thus producing spectacle appearance.
3. Remaining 15% cells have trilobed nucleus.
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Cytoplasm: i. Acidophilic, appears light pink in
colour after staining Granular ii. Granules1. Coarse, stain bright brick red with
acidic (eosin) dye.
2. Granules do not cover the nucleus.
3. They contain very high peroxidase content (histaminase), lysozymes, ECF-A & Major Basic Protein (MBP)
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FUNCTIONS:1. Mild Phagocytosis: less
motile than
neutrophils
2. Parasitic infestations: Major Basic Protein- Larvicidal Eosinophil Cationic Protein-
bactericidal & major destroyer of helminths.
Eosinophil Peroxidase – destruction of helminths, bacteria & tumour cells
FUNCTIONS:3. Allergic reaction:
bronchial asthma & hay fever
Detoxifying inflammation inducing subs like bradykinin, histamine
inhibit mast cell degranulation phagocytose & destroy Ag-Ab
complexes
4. Immunity: specially abundant in the mucosa of respiratory tracts, GIT, urinary tract, where they provide mucosal immunity
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VARIATION IN EOSINOPHIL COUNT
Eosinophilia: ↑ in eosinophils Causes are:-
1)Allergic conditions e.g. bronchial asthma, hay fever, filariasis
2) Parasitic infestation, trichinosis & schistosomiasis e.g. worms (hookworm, roundworm & tapeworm),
3) Skin disease like utricaria.
Eosinopenia: ↓ in eosinophils
Causes are:-
1) ACTH & steroid therapy
2) Stressful conditions, &
3) Acute pyogenic infections
BASOPHILS: Size:10-14 µm in diam. Nucleus:
irregular bilobed, often ‘S’
shaped & its boundary is not clear because
of overcrowding with coarse granules.
Cytoplasm: Is slightly basophilic & appear blue, it is full of granules.
Granules: coarse, stain deep purple/blue Plenty, completely fill the cell & overload the nucleus Contain heparin, histamine & 5HT.
FUNCTIONS 1. Mild phagocytosis
2. Role in allergic reaction: Basophils release histamine,
bradykinin, slow reacting substance of anaphylaxis (SRS-A) & serotonin (5HT). These substances cause local vascular & tissue reactions that cause many allergic manifestations.
3. Prevents spread of Allergic inflammatory process
4. Liberates heparin which i. Acts as anticoagulant & keeps blood in fluid state.
ii. Activates the enzyme lipoprotein lipase which removes fat particles from the blood after fatty meal.
VARIATION IN BASOPHIL COUNT: Basophilia: ↑ in basophil
count >100/mm3 Causes are:-
1) Viral infections, e.g. influenza, small pox & chicken pox
2) Allergic diseases
3) Chronic myeloid leukemia.
Basopenia: ↓ in basophil count
Causes are:-
1) Corticosteroid therapy,
2) Drug induced reactions &
3) Acute pyogenic infections
2nd line of defence. Size: Largest WBC 18-20 µm. Nucleus:
1. Is large single, eccentric in position (present on one side of the cell).2. It is notched/ indented (kidney shaped)3. It has reticulated chromatin network.
Cytoplasm: i. Is abundant, pale blue & usually clear with no
granules.Granules: i. Sometimes contain fine purple dust like
granules called Azur granules
FUNCTIONS1. Role in phagocytosis: These are powerful phagocytes & capable
of phagocytosis as many as 100 bacteria. They also have
ability to engulf large particles such as RBCs & malarial
parasites.
2. Role in tumor immunity: kill tumor cells after sensitization by lymphocytes, play a key role in the lymphocyte – mediated immunity.
3. Synthesis of Biological Substances: synthesis complement, prostaglandin E & clot promoting factors Interleukin1 ii) Hemopoietic factors iii) TNF-α, iv)Binding proteins like transferrin,v) lysosomes, Proteases vii) Acid hydrolases
VARIATION IN COUNTMonocytosis: ↑ in monocyte
countCauses are:-
1) Certain bacterial infections, e.g. tuberculosis, syphilis & subacute bacterial endocarditis
2) Viral infections
3) Protozoal & rickettsial infections, e.g. malaria, kala azar
Monocytopenia: ↓ in monocyte count
Causes are:-
It is rare, may be seen in hypoplastic bone marrow.
2 types of lymphocytes Morphologically: small & large Functionally: T & B lymphocytes
Small lymphocytes: 7-10 µm
Nucleus rounded, cytoplasm: just rim is seen. Older cells.
Large lymphocytes: 10-14 µm Nucleus is big with indentation, definite cytoplasm is seen. Precursor of small lymphocyte.
Functional subtypes: small lymphocytes are broadly classified into
1. B lymphocyte: processed in the bone marrow, concerned with the humoral immunity.
2. T lymphocyte: processed in thymus, concerned with the cellular immunity
Functions of B lymphocytes: B lymphocytes & their derivatives, plasma cells are responsible for humoral (antigen mediated) immunity. They produce antibodies (gamma globulins).This is major mechanism against the invading organisms
by direct action by making them inactive by agglutination, precipitation, neutralization or lysis and through complement system
Functions of T lymphocytes: T lymphocytes are responsible for cellular (Cell mediated/ T
cell) immunity. T cell immunity play imp defensive role against: viral & bacterial infections tumor cells
Provide a specific immune response toinfectious diseases.
VARIATION IN LYMPHOCYTE COUNTLymphocytosis: ↑ in
lymphocyte countPhysiological
1. healthy & young children
2. female during
menstruation
Pathological: 1. Chronic infections like tuberculosis,
hepatitis & whooping cough
2. Lymphatic leukemia
3. Viral infections like chicken pox
4. Autoimmune disease like thyrotoxicosis
Lymphocytopenia: ↓ in lymphocyte count
1. Patients on corticosteroid & immunosuppressive therapy
2. Hypoplastic bone marrow
3. Widespread irradiation
4. Acquired Immuno Deficiency syndrome (AIDS)
LIFE SPAN OF WBCS Granulocytes:
after released from bone marrow, 4-8 hours circulate in blood & another 4-5 days in the tissues. Survive only for few hours in serious infection
Monocytes: 72 hrs in blood. Once in tissue they swell up to much larger size to become
tissue macrophage → in this form they can live for month.(3) Lymphocytes:
Life span for week or months depending on body’s need. They continually circulate in blood & move from blood to
tissues & from tissues to blood and again blood to tissues.
LEUKAEMIAS Malignant diseases Increase in total WBC count->50,000/mm3 Presence of immature wbcs in peripheral blood
Types of LeukaemiasTypes of Leukaemias1. Acute myeloblastic leukaemia (AML)
2. Acute lymphoblastic leukaemia (ALL)
3. Chronic myeloid leukaemia (CML)
4. Chronic Lymphoid leukaemia (CLL)
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