Basophilic Myelocyte

Basophils develop from the multipotential myeloid stem cell (CFU-GEMM) which differentiates into basophilic progenitor cells (CFU-Ba).

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

Basophilic myelocyte is the first recognizable precursor of basophils.

• 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 basophilic, specific granules begin to accumulate
• Azurophilic granules
• Last cell capable of mitosis

It is difficult to find developing basophils because they account for less than 0.5% of granulocytes.

Example:

• Basophilic myelocyte (60x) [+]

Basophilic Metamyelocyte

The basophilic myelocyte matures into a basophilic 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
• Many very basophilic, specific granules
• Few azurophilic granules
• No longer capable of mitosis

Example:

• Basophilic Metamyelocyte (60x) [+]

Band Basophil

The basophilic metamyelocyte matures into a band basophil.

• Smaller cells (10 to 12 µm diameter)
• Nucleus is elongated and often has a horseshoe-like ("U") appearance that contains heterochromatin
• Cytoplasm is a pale blue-pink
• Many very basophilic, specific granules
• Few azurophilic granules
• No longer capable of mitosis

No band basophil is found on this slide.

Basophil

The band basophil develops into a mature basophil. Basophils mediate inflammatory responses.

• Rare white blood cells (<1%)
• Smaller cells (10 to 12 µm diameter)
• Nucleus bilobed or S-shaped
• Cytoplasm is a pale blue-pink
• Many very basophilic, specific granules
• Few azurophilic granules
• No longer capable of mitosis

Examples:

• Basophil #1 (60x) [+]

• Basophil #2 (60x) [+]

• Basophil #3 (60x) [+]