Eosinophilic Myelocyte

Eosinophils develop from the multipotential myeloid stem cell (CFU-GEMM) which differentiates into eosinophilic progenitor cells (CFU-Eo).

Eosinophilic myeloblasts are produced directly from progenitor cells (CFU-Eo) under the influence of cytokines. The eosinophilic myeloblast matures into an eosinophilic promyelocyte. These cells cannot be distinguished from cells at the same stage in other granulocyte lineages. (See MH034B Neutrophil Development for these earlier stages.)

Eosinophilic myelocyte is the first recognizable precursor of eosinophils.

• Large cells (18 to 20 µm diameter)
• Round, oval, or indented nucleus (50% of cell) with a coarser, granular pattern of chromatin
• Cytoplasm is pale blue
• Very eosinophilic, specific granules begin to accumulate
• Azurophilic granules
• Last cell capable of mitosis

Examples:

• Eosinophilic Myelocyte #1 (60x) [+]

• Eosinophilic Myelocyte #2 (60x) [+]

• Eosinophilic Myelocyte #3 (60x) [+]

• Eosinophilic Myelocyte #4 (60x) [+]

Eosinophilic Metamyelocyte

The eosinophilic myelocyte matures into an eosinophilic metamyelocyte.

• Smaller cells (12 to 17 µm diameter)
• Nucleus is dented, kidney shaped (50% of cell) of mostly heterochromatin
• Cytoplasm ranges from blue-gray to pink-gray
• Eosinophilic, specific granules that range from blue-gray to red
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Eosinophilic Metamyelocyte #1 (60x) [+]

• Eosinophilic Metamyelocyte #2 (60x) [+]

• Eosinophilic Metamyelocyte #3 (60x) [+]

Band Eosinophil

The eosinophilic metamyelocyte matures into a band eosinophil.

• Smaller cells (10 to 12 µm diameter)
• Nucleus is elongated and often has a horseshoe-like appearance that contains mostly heterochromatin
• Cytoplasm is a pale blue-pink
• Eosinophilic, specific granules that range from blue-gray to red
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Band Eosinophil #1 (60x) [+]

• Band Eosinophils #2 (60x) [+]

• Band Eosinophil #3 (60x) [+]

Eosinophil

The band eosinophil develops into a mature eosinophil. Eosinophils phagocytose immune complexes and kill bacteria.

• 12 to 15 µm diameter
• Nucleus is bilobed
• Cytoplasm is a pale blue-pink
• Eosinophilic, specific granules - oval, 1 to 1.5 µm diameter, red/orange
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Eosinophil #1 (60x) [+]

• Eosinophil #2 (60x) [+]

• Eosinophils #3 (60x) [+]

• Eosinophils #4 (60x) [+]

Mature eosinophils are released from bone marrow into the peripheral circulation. They circulate in the blood 8 to 16 hrs. Their tissue life span is only 2 to 5 days.