Eosinophils are granulocytic leukocytes that are involved in initiating and propagating many inflammatory responses, including those to parasitic infections and allergic diseases. They mature and are produced in the bone marrow, then migrate to mucosal tissues where they may play a role in preparing the uterus for pregnancy. Eosinophils contain orange-staining granules with cytotoxic proteins that can induce tissue damage, such as major basic protein, eosinophil cationic protein, eosinophil peroxidase, and eosinophil-derived neurotoxin.

1. Eosinophils
Anneka Pierzga & Geoffrey Latner | MLT 1042 | April 16, 2016 | College of Southern Maryland
Maturation
Hypersegmentation
What is an Eosinophil?
Eosinophilia
Chediak-Higashi Syndrome
• The Chediak-Higashi syndrome is a rare autosomal recessive
condition associated with abnormally large leukocyte granules
resulting from fusion of lysozymes. This disorder may affect
granulocytes, leukocytes, and monocytes (UVA).
• Phagocytosis is defective. Platelets lack dense granules and
platelet function is abnormal (UVA).
Bibliography
• Eosinophilia occurs in association with hypersensitivity
reactions, parasitic infestations, cancers (Hodgkin's
disease, eosinophilic leukemia). (Blumenreich, 1990, p.
726)
• Blood smear presents high percentage of eosinophils, as
shown in the picture above.
• A 100 cell differential count of 5 or more eosinophils is
the basis for diagnosing eosinophilia.
Pluripotent Stem Cell Myeloid Stem Cell CFU-GEMM
CFU-Eo
Myeloblast
Eosinophilic
Myelocyte
Eosinophilic
Metamyelocyte
Eosinophilic
Band
Eosinophil
Size: 12-18µm
Nucleus: round to
oval; may have 1
flattened side
Nucleoli: not visible
Chromatin: coarse;
more condensed than
promyelocyte
Primary Granules:
few to moderate
Secondary
Granules: variable
number of refractile
orange granules
N/C Ratio: 2:1 to 1:1
“Dawn of
Eosinophilia”
Size: 10-15µm
Nucleus: kidney
bean shape;
indentation < 50%
width of nucleus
Nucleoli: not
visible
Chromatin:
coarse, clumped
Primary
Granules: few
Secondary
Granules: many
orange, refractile
N/C Ratio: 1.5:1
Size: 10-15µm
Nucleus: constricted
but no threadlike
filament; indentation
>50% nucleus
Nucleoli: not visible
Chromatin: coarse,
clumped
Primary Granules:
few
Secondary
Granules: abundant
orange, refractile
N/C Ratio: cytoplasm
predominates
Size: 12-17µm
Nucleus: 2-5 lobes
connected by thin
filaments
Nucleoli: not visible
Chromatin: coarse,
clumped
Primary Granules:
rare
Secondary
Granules:
abundant orange,
refractile
N/C Ratio:
cytoplasm
predominates
IL-1, IL-6,
IL-3
GM-CSF
IL-3
GM-CSF,
IL-3
GM-CSF,
IL-5
GM-CSF,
IL-5
GM-CSF,
IL-5
Adapted from
Harmening, 2009
Adapted from
Carr & Rodk,
2013
Eosinophils are granulocytic leukocytes involved in the initiation and propagation of
many inflammatory responses, including those of parasitic helminth infections and
allergic diseases (Harmening 2009;Hogan and Rothenberg 2006). There is some
evidence that they may act as APCs. They have been implicated in hypersensitivity
reactions including allergic airway disease, asthma, eosinophilic gastritis and
esophagitis, and Celiac disease (Hogan and Rothenberg 2006, Dyer, Foster et al.
2013)
They are produced and mature in the bone marrow and are released into the blood,
where they migrate to mucosal beds such as the skin, GI tract, vagina, and bronchial
mucosa (Harmening 2009). Evidence suggests they may have a role in preparing the
uterus for pregnancy and blastocyst implantation (Hogan and Rothenberg 2006).
Eosinophils have orange-staining secondary granules which contain several cytotoxic
proteins capable of inducing tissue damage and dysfunction:
• Major Basic Protein – alters smooth muscle contraction responses and induces
mast cell and basophil degranulation
• Eosinophil Cationic Protein – shown to possess antiviral activity; induction of mast
cell degranulation, stimulation of airway mucus secretion, suppression of T cell
proliferation and IG synthesis by B cells
• Eosinophil Peroxidase – catalyzes oxidation of several substances to produce
highly oxidative substances that promote cell death
• Eosinophil-derived Neurotoxin – shown to possess antiviral activity (Hogan and
Rothenberg 2006)
• Eosinophils typically have up to 4 nuclear
lobes.
• Hypersegmentation occurs when more
than 3 eosinophils contain 5 lobes or 1
contains 6 or more lobes in a 100 cell
differential (UVA).
• This is sometimes called a “right shift”
(UVA).
• Hypersegmentation may accompany other
disorders that affect maturation