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WBCs or also known as Leucocytes are the colorless cells of the Blood. These cells do not contain Haemoglobin and thus are colorless. They do not have a fixed shape which enables them to move out of the capillaries by a process called Diapedesis.

The number of WBCs in the blood ranges from 6000-9000/mm3. An increase in number of WBCs is called Leucocytosis while decrease in its number is called Leucopenia.

The WBCs are divided into two groups on the basis of presence or absence of cytoplasmic granules (lysosomes containing different types of enzymes) i.e. Agranulocytes and Granulocytes.

1. AGranulocytes

These are the WBCs that do not contain cytoplasmic granules i.e. are agranular.

a. lymphocytes
  • Size- 7-8 μm (small lymphocytes) and 12-15 μm (large lymphocytes)

  • Formation- Formed by Lymphoblasts in the lymphatic tissues and bone marrow

  • Nucleus- Round

  • Functions- Synthesis of antibodies

  • DLC- 20-30%

  • Types- T-cells and B-cells

  • Size- 15-20 μm (Largest WBCs)

  • Formation- Formed by Monoblasts in the bone marrow and connective tissue

  • Nucleus- Kidney shaped

  • Functions- Phagocytosis

  • DLC- 4-8%


These are the WBCs that contain cytoplasmic granules. The formation of these cells occurs from the Myeloblasts.

A. Eosinophils
  • Size- 10-15 μm

  • Nucleus- Bilobed nucleus

  • Staining- Takes up acidic stains (also called Acidophils)

  • Functions- Produces antitoxins against allergens

  • DLC- 1-4%

  • Size- 10-15 μm

  • Nucleus- S shaped nucleus

  • Staining- Takes up basic stains like methylene blue

  • Functions- Produces Heparin and Histamines

  • DLC- 0-1% (least in number)

C. Neutrophils
  • Size- 10-14 μm

  • Nucleus- 2-7 lobed nucleus

  • Staining- Takes up neutral stains like neutral red

  • Functions- Phagocytosis

  • DLC- 60-65% (maximum in number)

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