White Blood Cells - Leukocytes

Leukocytes or WBCs are found in a thin grey layer known as the buffy coat in centrifuged blood. Above the leukocytes lie the platelets. Their role is primarily defensive. The different cells are seen in the table below

White Blood Cells/Leukocytes

• Neutrophils
  • Mature neutrophil (12-15u dia) is characterized by segmentation into 2-5 lobes.
  • Chromatin is dense and clumped with distinct lighter areas of parachromatin.
  • Cytoplasm contains variable numbers of light staining "neutral" granules and a few and a few azurophilic 1 granules, persistent from earlier stages.
  • Role is in the acute inflammatory process
• Eosinophils
  • Large orange granules of the eosinophil - easily recognised.
  • 12-15um diameter has chromatin similar to that of a neutrophil
  • Fewer lobes than neutrophil usually (2-3) lobes.
  • Normally 0-6% eosinophils are found in the peripheral blood.
  • Eosinophil specific granules contain Major Basic Protein (MBP)
  • Toxic to several parasites (helminths, microfilariae; schistosomiasis), and some mammalian cells.
• Basophils
  • Purple-black, often large coarse granules
  • Mature nucleus is segmented into 2-3 lobes.
  • 12-15u diameter
  • Contain Heparin and large amounts of histamine.
  • Active participants in hypersensitivity reactions.
• Monocytes
  • Largest (12-20u dia) cells normally found in the peripheral blood.
  • Blue-grey, sometimes very pale pink cytoplasm
  • Small, generally indistinct, granules.
  • large azurophilic granules will be seen.
  • Nucleus is irregular, frequently with delicate folds and often lobulated.
  • Chromatin is fine and lacey, sometimes described as reticular.
  • Phagocytes and frequently contain vacuoles
  • Monocytes can migrate into tissues where they are known as macrophages.
  • Important role in inflammatory processes.
  • Peripheral blood normally contains 0-l0% monocytes.
• Lymphocytes
  • Vary greatly in size (7-20m dia) and in nuclear and cytoplasmic character.

Causes of a raised WCC

• Acute or Chronic myeloid leukaemia
• Acute lymphoblastic leukaemia
• Chronic lymphocytic leukaemia
• Lymphoma
• Myeloma
• Myelofibrosis
• Infection
• Corticosteroid therapy
• Brisk GI tract bleeding
• ‘Stress’, e.g. postoperative
• Post splenectomy

Worrying features ? malignant

• Sepsis, Ill patients, Bleeding, Bruising, Petechiae
• Enlarged liver or spleen or lymph nodes
• Weight loss, Bizaree features on blood film

References

• University of Virginia Teaching Site