Neutrophil

• Morphology
  • Size- 10-15 microns
  • Nucleus has 2-5 distinct lobes and coarse chromatin
  • Abundant cytoplasm with fine, pink/violet-pink granules
• Half-life in blood is 7hrs, while they function in tissues for 1-2 days.
• 0.85-1.6x10⁹ neutrophils/Kg are produced every day
• Death of neutrophils occurs by apoptosis
• Types of granules (Contents of granules change as the cell matures)
  • Primary (azurophilic)- Contain myeloperoxidase, lysozymes, defensins etc.
  • Secondary (specific)- Contain collagenase, sialidase, lactoferrin etc
  • Tertiary (Gelatinase)- Contains gelatinase, acetyl transferase and lysozyme
  • Secretory vesicles 

Eosinophil

• Morphology
  • Size- 10-15 microns
  • Nucleus has 2-3 distinct lobes and coarse chromatin
  • Abundant cytoplasm with large, coarse, uniform sized, crimson red numerous granules
• Half-life in blood is 18hrs, while in tissues they may live for several weeks.
• Death occurs due to apoptosis, which is enhanced by glucocorticoids.
• Proteins present in the granules:
  • Major basic protein
  • Eosinophil cationic protein
  • Eosinophil peroxidase
  • Eosinophil derived neurotoxin
• They help in control of parasitic infections

Basophil

• Morphology
  • Size- 10-15 microns
  • Nucleus has 2-3 distinct lobes and coarse chromatin, nuclear details are obscured by granules
  • Abundant, cytoplasm with large, coarse, uniform, bluish-black granules.
• Granules are metachromatic and contain histamine and heparin
• They mediate immediate hypersensitivity reaction 

Monocyte

• Comprise 1-9% of WBCs
• Normal absolute count: <1000/cmm
• They mature to form macrophages
• Immunophenotype: CD45+, CD4+, CD68+, CD163+ and lysozyme+
• Macrophages form the mononuclear phagocyte (reticulo-endothelial) system which consists of 
  • Kupfer cells in liver
  • Alveolar macrophages in lung
  • Littoral cells in spleen
  • Langerhans cells in skin
  • Microglial cells in brain
  • Macrophages in bone marrow
  • Osteoclasts in bone
  • Type A cells of synovium
• Functions of these cells include:
  • Phagocytosis and degradation of both soluble and particulate substances
  • Act as antigen presenting cells
  • Stimulate proliferation of lymphocytes through release of various cytokines
  • Removal of cells that have undergone apoptosis
• Dendritic cells:
  • Have projecting cytoplasmic dendrites.
  • Process antigens for presentation to T cells
  • Subtypes include:
    • Langerhans cells: S100 protein+, CD1a+, CD207+, CD4+
    • Indeterminate dendritic cells: S100 protein+, CD1a+, CD207-, CD4+
    • Interdigitating dendritic cells: S100 protein+, CD1a-, CD207-, CD4+
    • Interstitial dendritic cells: Fascin+, factor XIIIa+, CD4+/-
• Plasmacytoid dendritic cells
  • Immunophenotype: CD123 (IL-3R)+, CD303, (BDCA2)+, CD304 (BDCA4)+, TCF4+ 
  • Play role in antiviral immunity and systemic autoimmunity

Figures:

Figure 1.3.1 - Neutrophil

Figure 1.3.2 - Eosinophil

Figure 1.3.3 - Basophil (Arrow)