white blood cells · properties of white blood cells neutrophils can attack and destroy bacteria in...

White Blood Cells

By:

Dr Asma Jabeen

▪ Also called leukocytes

▪ Mobile units of body’s protective

system

▪ Most of them are specifically

transported to areas of serious infection

and inflammation thereby providing a

rapid and potent defense against

infectious agent

White Blood Cells

Leukocytes

Granulocytes Agranulocytes

Polymorphonuclear• Neutrophil• Eosinophil• Basophil

• Lymphocytes

• Monocytes

White blood cells

Granulocytes Non-GranulocytesNeutrophils MonocytesEosinophils LymphocytesBasophils

Polymorphonuclear MononuclearNeutrophils MonocytesEosinophils LymphocytesBasophils

Phagocytes Non-phagocytesNeutrophilsMonocytes LymphocytesMacrophagesEosinophils Basophils

Neutrophils 62%

Lymphocytes 30%

Monocytes 5.3%

Eosinophils 2.3%

Basophils 0.4%

Never Let Monkeys Eat Bananas

Genesis of WBCs

Genesis of white blood cells. The different cells of the myelocyte series are 1, myeloblast; 2, promyelocyte; 3, megakaryocyte;4, neutrophil myelocyte; 5, young neutrophil metamyelocyte; 6, “band” neutrophil metamyelocyte; 7, polymorphonuclear neutrophil; 8,eosinophil myelocyte; 9, eosinophil metamyelocyte; 10, polymorphonuclear eosinophil; 11, basophil myelocyte; 12, polymorphonuclear basophil;13-16, stages of monocyte formation.

Myeloblast

Promyelocyte

Neutrophil myelocyte

Young neutrophil metamyelocyte

Band neutrophilmetamyelocyte

Polymorphonuclearneutrophil

▪ Granulocytes ,monocytes are formed

only in bone marrow▪ Lymphocytes, plasma cells are formed

in spleen, lymph nodes, thymus etc▪ WBCs stored in the bone marrow until

needed in the circulatory system(3 times the quantity as circulate in entire blood)

Life Span of WBCs

➢ 4 to 8 hrs circulating in the blood and 4 to 5 days in tissues where they areneeded.

➢ Serious infection shortens life span

➢ Monocytes 10 to 20 hrs in blood, after that wander to tissues, can live for months as tissue macrophages

Properties of white blood cells

▪ Neutrophils can attack and destroy

bacteria in circulating blood

▪ Tissue macrophages begin life as monocytes (little ability to fight infections) but in tissues are extremely capable of combating intra tissue diseaseagents

Margination

White blood cells

align themselves

along the vessel wall

before leaving the

vessel.

• Neutrophil attracted by glycoproteins(selectins) on endothelial cells

• Adhesion

• Emigration that is

purposeful, directed

and ameboid

Diapedesis

▪ Neutrophils &

monocytes can

squeeze through

pores of blood

capillaries

Ameboid motion

▪ Neutrophils and macrophages can

move through tissues by ameboid

motion

▪ Some cells move through tissue spaces

at velocities 40µm/min

Chemotaxis

Chemical substances in the tissues cause

neutrophils and macrophages to move

towards the source of the chemical.

▪ Depends on concentration gradient of

chemotactic substance

▪ Effective upto 100 µm away from

inflamed tissue

Chemotactic substances

• Bacterial or viral toxins

• Degenerative products of the inflamed tissues themselves, leukotriens and chemicalsreleased from lymphocytes, basophils and mast cells

• Several reaction products of complement themselves(C5a)

• Several reaction products caused by plasma clotting in inflamed area (activated factor XII)

Phagocytosis

➢ Cellular ingestion of the offending agent.

➢ Most important function of the neutrophils and macrophages

Why phagocytosis is selective?

▪ Smooth surfaces of natural tissues

resist phagocytosis

▪ Protective protein coats of natural substances repel the phagocytes

▪ Antibodies (IgG) adhered to bacteria makethem susceptible for phagocytosis

▪ Presence of Complement (C3b) moleculeson bacteria

The selection and phagocytosis process

is called OPSONIZATION.

Phagocytosis by neutrophil

• Neutrophil attaches to cell and projects

pseudopodia• Fusion of pseudopodia and formation of

enclosed vesicle• Free floating phagocytic vesicle • A single neutrophil phagocytize 3 to 20

bacteria

Phagocytosis by macrophage

• Much more powerful than neutrophil

• Capable for phagocytizing 100 bacteria• Engulf larger particles like RBC, malarial

parasites• Extrude the residual products and

survive for many more months

• Lysosomes filled with proteolytic enzymesfuse with phagosome to make it a digestivevesicle.

• Lipases in macrophages

Bactericidal agents help in killing bacteria Oxidizing agents by peroxisomes

▪ Superoxide

▪ Hydroxyl ions▪ Hydrogen peroxide▪ myeloperoxidase

Thank you