Bone marrow nonneoplastic



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Last staff update: 28 September 2023

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PubMed Search: Basophils [title] bone marrow

Dragos C. Luca, M.D.
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Cite this page: Luca DC. Basophils. website. Accessed November 29th, 2023.
Definition / general
  • 0.5% of all white blood cells (least numerous granulated cells in peripheral blood)
  • Named because it stains with basic dyes
  • Similar to mast cells but apparently generated by different CD34+ precursor cells in bone marrow (basophils mature in marrow, mast cells in connective tissue)
  • Progresses from the multipotent myeloid stem cell via a committed progenitor (basophil colony forming unit, CFU-Baso) to basophilic promyelocyte, to basophilic myelocyte, to basophilic metamyelocyte, to basophil
  • Leaves bone marrow as terminally differentiated granulocyte
  • Basophils and mast cells are effector cells in allergen / IgE mediated immune responses
  • They induce type 1 immediate immune response in airways and elsewhere, causing bronchial asthma and other allergic diseases (Allergol Int 2006;55:105)
  • Also play a critical role in host defense against helminths (Allergol Int 2006;55:99)
  • Factors thought to play key role in basophil production: IL3 (main cytokine), GM-CSF, IL4, IL5 (primary cytokine linked to specific eosinophil and basophil production), stem cell factor (SCF)
  • Basophils and their granules contain histamine, sulphated mucopolysaccharides (mostly chondroitin sulfate), peroxidase, low levels of chymase, negligible amount of tryptase, Charcot-Leyden crystal protein, PAF and ECF-A
Clinical features
  • Basophil activation test, using CD203c or CD63 as an activation marker, has become a reliable test for in vitro investigation of immediate allergy, complementing other in vitro tests (Clin Mol Allergy 2005;3:9)
  • Significant basophilia is more likely to represent neoplasia (chronic myelogenous leukemia, other chronic myeloproliferative disorders, myelodysplastic syndromes, acute leukemias) than reactive processes
  • Nonneoplastic basophilia: allergic / hypersensitivity reactions, hypothyroidism, ulcerative colitis, rheumatoid arthritis, renal disease, rare infections (varicella, influenza), irradiation, rare carcinomas and rare drugs (estrogens, antithyroid agents)
  • Decreased number of basophils (basophilopenia): certain medications (steroids, epinephrine, thyrotoxicosis therapy), acute stress, acute inflammation
Microscopic (histologic) description
  • Basophilic granules are metachromatic (reddish purple) with Toluidine blue and Alcian blue; are also water soluble
  • Basophilic myeloblast: difficult to distinguish from other granulocyte blasts; large round cell with basophilic cytoplasm without granules; N/C ratio is 80%; dispersed chromatin with nucleolus
  • Basophilic promyelocyte: intermediate in development between basophilic myeloblast and myelocyte; large round cell with a few undifferentiated cytoplasmic granules; slight chromatin clumping, nucleolus present
  • Basophilic myelocyte: round / oval cell; cytoplasm with slight basophilia, moderate cytoplasmic purple black granules of varying size and shape; granules are usually larger than neutrophilic granules; N/C ratio is 50%; chromatin moderately condensed, no distinct nucleolus
  • Basophilic metamyelocyte: oval cell with abundant pale cytoplasm, large and fairly uniform specific granules; N/C ratio is 40%; nucleus is small and indented with condensed chromatin, no nucleolus
  • Basophil: smaller than other white blood cells (10 - 15 microns); cytoplasm is homogenous pale blue but often obscured by purple blue granules (containing heparin and histamine); N/C is 20%; nucleus is often unsegmented or bilobed, chromatin is coarse
Microscopic (histologic) images

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Basophilic myelocyte

Basophilic myelocyte

Basophilic metamyelocyte

Basophilic metamyelocyte

Peripheral smear images

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Positive stains
Negative stains
Electron microscopy description
  • Granules ~20nm in diameter with a particulate substructure
Electron microscopy images

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