Histology of blood cells

• Jeanne Adiwinata Pawitan

• Department of Histology FMUI

Blood – 5 lt

• Specialized connective tissue – circulate – logistical support, communication

• Component:° Blood plasma - serum° Cells• Erythrocytes (45%)• Leucocytes – (polymorphonuclear,

mononuclear) 1%

° Platelets

Leukocytes

• Polymorphonuclear (granular→ granulocyte)° Basophilic leukocytes (basophils)° Eosinophilic/acidophilic leukocytes (eosinophils)° Neutrophilic/heterophilic /polymorphonuclear

leukocytes (neutrophils, polys)

• Mononuclear (agranular→ agranulocyte)° Monocytes ° Lymphocytes• B lymphocytes• T lymphocytes

Leucocyte granules• Nonspecific (azurophilic) granules–0.5μm

- all leucocytes• Specific granules – Giemsa/Wright° Neutrophils • Small specific granules (0.1 μm– light pink)• Tertiary granules

° Eosinophils – specific granules (oblong:1-1.5 μm >< 1 μm ) - dark pink

° Basophils –specific granules (0.5 μm-blue-black)-pressed to periphery →rough

Azurophilic granules• = lysosomes contain:° Acid hydrolase° Myeloperoxidase° Lysozyme (antibacterial agent)° Bactericidal permeability increasing (BPI)

protein° Cathepsin G° Elastase, Nonspecific collagenase

→ extracellular matrix →tissue damage

Neutrophils

• Most numerous → 60-70 % total leuco-

• Ø 9-12 μm (in blood smears)

• Nucleus ° multilobes – chromatin threads, age ↑- lobe↑° ♀- drumstick/Barr body - condensed,

inactive, 2nd X chromosome

• ↑- acute bacterial infection

Neutrophil’s specific granules

• Small specific granules:° Enzymes antimicrobial function

° Pharmacological agent facilitate migration

• Tertiary granules-neutrophil chemotactic agent→release: ° Gelatinase-degrades basal lamina - facilitate migration

° Cathepsins

° Glycoproteins – inserted to plasmalemma – facilitate phagocytosis

Neutrophil’s function

• Phagocytosis – microorganism → microphage• Kill bacteria by° Enzymes° Forming reactive Oxygen compounds

→ die → (dead leuco, bacteria, tissue fluid)• Synthesize leucotrienes (from arachidonic

acid-in their cell membrane) – aid in initiation of inflamation

Phagocytosis

Phagocytosis

↓

phagosome → destroyed(intracellular vacuole) ingested microorganism

↑

Azurophilic granules (lysosome)

Reactive oxygen compounds

• Superoxide - formed in respiratory burst (by NADPH oxidase)

• Hydrogen peroxide formed from superoxide (by superoxide dismutase)

• Hypochlorous acid (HOCP) formed from hydrogen peroxide and chloride ions (by myeloperoxidase)

Eosinophils• < 4 % - total leuco-• Ø 10-14 μm• Nucleus – bilobe• Plasmalemma rec -

binds to ° Histamin

° Leucotrienes

° Eosinophil chemotactic factor

release by mast cells, baso-, neutro-

→ Migrate to site of° Allergic reaction

° Parasitic worm invasion

° Inflammatory reaction

Eosinophil’s specific granules

• EM: ° center (=internum) – crystal like –electron

dense – contains:• Major basic protrein form pores in• Eosinophilic cationic protein parasites’ pellicle• Eosinophil derived neurotoxin

° Externum – less electron dense- contains:• Histaminase• Peroxidase, & other enzymes

Eosinophil’s function

• Kill parasites-by facilitating access of superoxide, hydrogen peroxide via pores in pellicles

• Release histaminase & other substances → inactivate initiators of inflamation° Histamine

° Leucotriene C

• Engulf Ag-Ab complex → endosomal compartment → degradation of Ag-Ab complex

Basophils

• < 1% total leuco-

• Ø 8-10 μm

• Nucleus – S shaped – masked by specific granules

• Plasmalemma – surface receptors – e.g. Ig E receptors → binds IgE (from plasma cells)

Basophil’s specific granules

• Specific granules contain:° Heparin° Histamine • Vasodilation

• Smooth muscle contraction (in the bronchial tree)

• Leakiness of blood vessels

° Eosinophil chemotactic factor° Neutrophil chemotactic factor° Peroxidase

Basophil’s functions

• IgE – Ag →° content of specific granules released° Phospholipase - phospholipids (in

plasmalemma) → arachidonic acids → leukotrienes C4, D4, E4 (=slow reacting substance of anaphilaxis, SRS-A) → • similar effects with histamine, but the action is

slower, and more persistent

• Activate leuco- →migrate to site of Ag challenge

Lymphocyte • 20-25% - total leuco-• Blood smears° Round, pleomorphic – conective tissue° Nucleus • round –slightly indented – occupies most of the cell• acentrically located • dense- heterochromatin>>>

° Cytoplasm – light blue • azurophilic granules = lysosomes• Mitochondria-few, Golgi App- small, RER-few,

ribosomes >>>

Lymphocyte

Size • Small Ø 8-10 μm• Medium Ø 12-15μm less numerous• Large Ø 15-18μmType (functional)• B lymphocytes – 15 % - months immuno• T lymphocytes - 80 % - years cytochem• Null cells (surface

markers)

Lymphocyte functions

• In connective tissue (not in blood)° Immune system• B lymphocyte – bone marrow immuno-

• T lymphocyte – thymus (cortex) competent

(maturation) →lymphoid system →mitosis →clone Memory cells – ready for subsequent Ag chalengeEffector cells → respond to Ag

Effector cells• B cells diff→ plasma cells - Ab• T cells – cellular immune system diff →° Cytotoxic T cells (CTL, T killer cells) – contact –

kill• Foreign cells• Virally altered cells

° T suppressor cells →signaling molecules° T helper cells (cytokines, lymphokines) Suppression/→specific response of other cells in

immnune system

Monocyte • 3-8% -total leuco-• 12-15 μm • Circulation – few days → connective tissue -

macrophage• Nucleus- large, acentric, kidney shaped° Chromatin network- coarse – 2 nucleoli →moth

eaten/soap buble appearance

• Cytoplasm – bluish gray° Azurophilic granules

° Vacuole-like spaces

Monocyte

ME

• Cytoplasm ° Organels ° Periphery• Microtubules

• Microfilaments

• Pinocytotic vesicles

• Filopodia

Monocyte-functions• →macrophage° Phagocytosis - phagosome – enzymatic digestion,

superoxide formation→ destruction• Cells (dead, defunct)

• Ag

• Foreign particulate matter (bacteria)

° APC – epitope (most Agnic) + class II HLA/MHC

° →foreign body giant cells – large foreign particle

° Cytokines• activate inflamatory response

• → proliferation, maturation of other cells

Platelets/thrombocyte/thromboplastids

• 250,000-400,000/mm3 blood• Life span < 14 days• Disk shaped - Ø 2-4μm • Cytoplasmic fragment–megakaryocyte-bone marrow• LM° Hyalomere – periphery - clear

° Granulomere - central – darker

• Plasmalemma° Glycocalyx (15-20 nm)

° Receptor molecules

Platelets – EM - hyalomere

• 10-15 microtubules (MT)-parallel → a ring – diskoid morphology

• Actin, myosin monomers – associated to MT – assembly →contractile apparatus

• Tubular system• Surface opening (connecting) – molecule rapid

uptake & release from activated platelets

• Dense tubular system – sequester Ca? >< platelet stickiness?

Platelets – EM - granulomere• Few organels° Mitochondria ° Peroxisomes

• Glycogen deposits• Enzymes ° Catabolize glycogen° Consume O2° Generate ATP

• Granules (α, δ, λ)

Platelets - granules

• α granules – 300-500 nm –contains° Fibrinogen° Platelet derived GF° Platelet thromboplastin° Thrombospondin° Coagulation factors

• α granules content → facilitate ° Vessel repair° Platelet aggregation – blood coagulation

Platelets - granules

• δ granules (dense bodies) – 250-300 nm - contains° Ca, ADP, ATP platelet aggregation ° Serotonin, histamine & adhesion, blood ° Pyrophosphatase coagulation

• λ granules (lysosomes) – 200-250 nm – contains ° hydrolytic enzymes →clot resorption

Platelets - functions

• Injury → limit hemorrhage ° Platelets → activated° Tissue factors - plasma born factors –

platelet derived factors → blood clot

Normal • Endothelium intact –

inhibit platelet aggr.° Prostacyclins

° NO2

• Endothelium luminal plasmalemma – inactivate specific coagulation factor° Thrombomodulin

° Heparin – like molecule

Injury• Endothelium° Stop producing

inhibitors

° Von Willebrand factor →platelet activation

° Tissue thromboplastin

° Endothelin→vasoconstr

• Endothelial disruption → platelet - collagen → platelet activated → → → → → → blood clot

Platelet - activated• Content of granule – released ° ADP platelet - sticky

° thrombospondin

→Platelet adhesion (to damaged vessel wall)

→Platelet aggregation o Plug – block hemorrhage

o Plasmalemma - platelet factor 3 = phospholipid surface – assembly of coagulation factors esp. thrombin

• Arachidonic acid (plasmalemma)→ thromboxane A2 ° Potent vasoconstrictor

° Platelet activator

Cascade of reactions in clot formation

Platelet & tissue thromboplastin

↓

Prothrombin → thrombin (enzyme)→pl aggr

+ Ca

Fibrinogen → fibrin –reticulum of clot

+blood cells, platelets

blot clot (thrombus)

Thrombus (blot clot) formation

• Erytrhrocytes – facilitate – platelet activation

• Neutrophils limit platelet activation• Endothelium & thrombus size• After clot formation ° 1 hour → clot contraction – ½ size → pulling

edges → minimize blood lost° Repair of blood vessel → lysis of thrombus

Thrombus (blood clot)

Contraction• Actin monomers →

thin filaments• Myosin monomers →

thick filaments• ATP – actin-myosin

filaments interact → contraction

Lysis • Vessel repaired →

endothelium – plasminogen activators

plasminogen → plasmin + λ gr.

enzymes lysis of thrombus