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Physiological Functions

of

White Blood cells

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Objectives: WBCs

1. Identify the different types of WBCs

2. Enumerate the functions of the various types of

WBCs

3. Describe the steps of formation of WBCs4. List the factors required for their maturation.

5. Infer the importance of total and differential

WBC counts

6. Define the terms leucocytosis and leucopenia7. Define leukemia

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White Blood Cells (WBCs Total Leucocyte count (TLC)

4000-11,000 /L

Types of WBCsGranulocytes contain granules

Neutrophils

Eosinophils

Basophils:

Agranlocytes

Lymphocytes

Monocytes

Differential count: DLCNeutrophils 60-70%

Lymphocytes 20-25%

Monocytes 3-8%

Eosinophils 1-4%Baso hils 0-1%

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Neutrophils 60-70%

10-12 in size; 2-5 lobed nucleus; Older the cell more the lobes-

(polymorphonuclear leukocytes);Small colored granules which contain enzymes, Defensins, oxidants

Action: by Phagocytosis

Life span: a few hrs: 4-8 hrs in blood; 4-5 days in tissuesFast response; neutrophilia in bacterial diseases; neutropenia in drug toxicity

Eosinophils 0-4%; 10-12 Bi-lobed nucleus; coarse acidophilic granules

Phagocytose antigen-antibody complexes; destroy parasites

Granules contain various enzymes : MBPIncrease in allergic conditions; decrease during stress-corticoids

Basophils 0-1% 8-10

Nucleus usually bi-lobed;large deep purple colored granules which often cover the nucleus

Secrete heparin, serotonin, histamine: help in inflammation

The Granulocytes 4

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Agranular WBCs

Monocyte 12-20 ;3-8%; circulate in blood for about 20-30 hrs.

long life span (many weeks to months) after change into macrophages intissues

Single kidney shaped nucleus

Phagocytosis after converting in to macrophages

Lymphocyte 6-9 (small); 10-14 (large); 20-25%; mostly formed inlymhoid tissue; some in bone marrow.

Nucleus surrounded by thin ring of cytoplasm; long life span inside tissues,

but only a few hours in blood

B and T lymphocytes:Immune mechanismsB lymphos form plasma cellsNatural Killer (NK) cells against viruses, cancer

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Physiology and Functions of WBCs

Life span: few hours to a few days

They have Major Histocompatibility Antigens on surface:

-Identification of the SELF

Main functions:

combat infection by phagocytosis immune mechanisms

Adhesion molecules

Selectins: on endothelial cells - attach to CHOnon neutrophil surface

Integrinson neutrophils: also makeWBCs stick to endothelial surface, &

help them to move out of the blood vessels

When required , they escape from the blood viacapillary pores (emigration) helped by integrins

enter tissue and have their action there byphagocytosis

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Ph i

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Phagocytosis

Mainly by neutrophils and monocytes

Steps of Phagocytosis

1 . Chemotaxis :attraction of WBCs to site of infectionPromoted by

i. bacterial toxins

ii. kinins from damaged tissues

iii. CSFs

2. Adherence

phagocyte attaches to microbe using proteins

3.Ingestion

pseudopods from WBC surrounds microbe

formation of a PHAGOSOME

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4. DigestionPhagosome enters cytoplasm of WBC and merges with LYSOSOME: Phago-

lysosome: secretion of lysozomal enzymes followed by release of oxidants:

oxidative burst5. Killing as result of the above. Residual bodies get left behind

1 MicrobeCHEMOTAXIS

Lysosome

Digestiveenzymes

Pseudopod

Phagocyte

ADHERENCE INGESTION

Plasmamembrane

DIGESTION

KILLINGResidual body(indigestiblematerial)

Digested microbe

in phagolysosome

2 3

4

5

Phases of phagocytosis8

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Formation of WBCs: Hemopoiesis

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Pluripotent stem cell

Lymphoid stem cellMyeloid stem cells

Colony Forming Unit

G/M

Eosinophilic

myeloblast

Basophilic

myeloblast

Neutrophil

monocyte

eosinophil

basophilNK lymphoblast

T lymphoblast

B lymphoblast

T

lymphocyte

B

lymphocyte

NK

Cell

Granulocytes and monocytes : formed only in the BONE MARROW stored in the bone marrow, andreleased into circulation. Lympocytes and Plasma cells also in lymhoid tissue, are stored in lymhoid

tissue . Few released into circulation

Various Colony Stimulating factors (CSFs or Growth Inducers) help in their formation:

IL1, IL6 and IL3 (multi CSF)

These are proteins in nature 10

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Normal WBC count: 4000-11000

Leuocytosis >11000

Some viral infections

Bacterial infections (typhoid)

Bone marrow suppression

Drugs: antibiotics

corticosteroids

Leuopenia < 4000

Neutophils

Infections, Burns, inflammation

Lymphocytes

Viral infections

Monocyts

Viral, fungal infections, TB,

Chronic disease

Eosinophils

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T i l

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Typical eg:

8 year child; high fever;

pain throat; difficulty in swallowing

swollen septic tonsils

TLC 18,500

DLC: N. 88%; L 10%; E 2%

Elderly person; exposure to radiation

Hx of intractable fever and infections;Loss of appetite

TLC 2000

DLC: N. 30% L 60%; E 4% ;

6% other WBCs

Leukemias(blood cancer)

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Summary

1. TLC, types of WBC, DLC

2. Description of various types of WBCs and their actions

3. Phagocytosis

4. Development of WBCs and factors associated5. Define leucocytosis/leucopenia with typical examples

6. Leukemias or blood cancer

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