EM 387 Eosinophil

Eosinophil

Transmission electron microscopy (TEM) of a transverse section through the surface epithelium of the small intestine. Besides the edges of enterocytes, both an eosinophil and a neuroendocrine cell are also seen.

• Enterocytes (intestinal absorptive cells; dark green) - simple columnar epithelial cells that line the inner surfaces of the small and large intestines.
  • Lateral Surface (#1,#2)- their lateral cell membranes form folds and projections that interdigitate with neighboring cells
    • Structural role in binding the cells into a continuous sheet
    • Increase the surface area available for absorbing nutrients from the intestinal lumen.
• Eosinophil (green) - white blood cells found in the blood that migrate into tissues, including the intestinal epithelium.
  • Crystalloid Granules (orange) - abundant large, specific granules (0.5 to 1.5 um in diameter) with an ellipsoid shape and a linear, crystalline core
    • Crystalloid core is composed of major basic protein
    • Matrix contains eosinophil peroxidase, eosinophil cationic protein, along with cytokines, chemokines, and enzymes (such as RNase and DNase)
  • Play a vital role in protecting the epithelium from parasites and allergens.
• Neuroendocrine Cell (tan) - scattered endocrine cells found in the intestinal epithelium
  • Express markers for both epithelial cells and neurons
  • Small, dense-core granules (purple)
  • Release peptide hormones into the capillary network beneath the epithelium

Subcellular Structures

• Nucleus (blue) / Nuclear Envelope (purple)
• Mitochondria (red)
• Endoplasmic Reticulum (cyan)
• Cytoplasm (dark green/green/tan)

Eosinophilic esophagitis is a chronic condition characterized by the infiltration of eosinophils into the esophageal epithelium. It can cause symptoms such as difficulty swallowing and chest pain.