White Blood Cells Prepared by Dr. Hamad ALAssaf [email protected] 2015.

White Blood Cells

Prepared by Dr. Hamad ALAssaf

[email protected]

Leukocytes / White Blood Cells

Granulocytes (65%)- neutrophils, eosinophils, basophils

- formed in bone marrow

Monocytes (5%)- tissue macrophages

- formed in bone marrow

Lymphocytes (30%)

- formed in lymph tissue

- life span: hours to years

Leukocytes Classification

• Granulocytes Non- Granulocytes– Neutrophils - Monocytes– Eosinophils - Lymphocytes– Basophils

• Polymorphonuclear Mononuclear– Neutrophils - Monocytes– Eosinophils - Lymphocytes– Basophils

• Phagocytes Non-phagocytes– Neutrophils, monocytes - Lymphocytes– Macrophages, eosinophils - Basophils

Phagocytic Cells

1- Polymorphonuclear Neutrophils- non-dividing, short-lived (6 hours to a few days)

- dominant number in bloodstream

2- Monocytes/Macrophages- long-lived cells (months)

- do not circulate

- present in tissue, particularly in lungs, spleen, liver, lymph nodes

- tissue macrophage system

Actions of Phagocytic Cells

1. Margination

2. Diapedesis

3. Ameboid Motion

4. Chemotaxis

5. Phagocytosis

Actions of Phagocytic Cells

1. Binding

2. Engulfment

3. Phagosome formationAcidificationproteolysis

4. Lysosome fusion

5 Membrane disruption

6-Antigenpresentation

MHC II

Phagocytosis

Cell-mediated Response to Inflammation

1. Tissue macrophages:

- already present in tissue

2. Neutrophil invasion:

- margination, diapedesis, chemotaxis

- stimulation of bone marrow to release stored leukocytes, 4-5 hours

3. Macrophage proliferation:

- invasion by circulating monocytes (several hours to increase size)

4. Stimulation of granulocyte and monocyte production:

- growth factors produced by tissue macrophages (TNF, IL-1, Cell stimulating factor)

Increased Transmigration

Blood vessel

Tissue Site of inflammation

Blood vessel

TissueTransmigration

Circulating and marginated pools

NORMAL PRODUCTION INFECTION

Marrowpool

Bone BoneIncreased circulationIncreased margination

Production IncreasedProduction

Decreasedmarrow pool

Granulocytes

• EOSINOPHILS:

- ~ 2% of total white blood cells

- active against parasites, skin diseases, chronic infections

- phagocytic and immunomodulatory, decrease inflammation

- life span 5 days

• BASOPHILS:

~ 0.5% of total white blood cells

- basophils similar to mast cells

- release primarily histamine, some bradykinin

- release due to binding of IgE

- Life span a few hours to a few days

Important terms

• Leukopenia : decrease in the number of white blood cells. example: bone marrow suppression

• Leukocytosis : increase in the number of white blood cells. example : bacterial infections

• Leukemia : (cancerous) uncontrolled production of white blood cells

Neutropenia

Neutropenia: decreased number of neutrophils due to:

Decreased production Increased neutrophil destruction (chronic infections)

Agranulocytosis: severe neutropenia due to:

production failure due to irradiation exposure to chemicals drugs

Immunity

It is a special defense mechanism which is mobilized when the body is invaded by a foreign organism.

Immunity

Innate = (present since birth)

- ability to resist damaging organisms and toxins - skin, gastric acids, tissue neutrophils and macrophages, complement

Acquired = (developed by exposure to specific invading agents).

- humoral ----> circulating antibodies - cellular ----> activated cells

Sequence

- Dormant lymphocytes

- Invasion of body by foreign antigen

- Phagocytosis by macrophages

- Presentation of antigen to lymphocytes

Antigen

An antigen: is a substance that can induce an

immune response when introduced into an

immunocompetent host and that can react with the

antibody produced from that response.

Bone MarrowStem cell

Pre-BCell

Pre-TCell T-Cell

T8-supressor

T4-helper

B-Cell Plasma Cell

IgG IgA IgM IgD IgE

LymphocytesT- and B-Cells

Thymus

Liver and Bone

marrow

T-cells

Cytotoxic Cellskill infected cells

Helper Cells ( CD-4 cells)activate macrophages and B-cells

Suppressor Cellsregulate activity