This document discusses eosinophils and eosinophilia. It begins with two case studies, one involving a 57-year-old man with a history of asthma and eosinophilia, and another involving a 28-year-old man diagnosed with hypereosinophilic syndrome after presenting with heart failure and marked eosinophilia. It then provides information on what eosinophils are, their role in the immune system, common causes of eosinophilia including allergies, parasites, and certain drugs. It discusses different subtypes of hypereosinophilic syndrome and their treatment options. It concludes by explaining how eosinophil activation can lead to tissue damage in some individuals with eosinophilia

1. Eosinophils and eosinophilia
Amy Klion

2. Disclosure
Employment
– National Institutes of Health
Financial Interests
– None
Research Interests
– GlaxoSmithKline, MedImmune
Organizational Interests
– Member of ASTMH, IES, IDSA
Gifts
– Nothing to Disclose
Other Interests
– Nothing to Disclose

3. Case 1
57 year old man with history of mild asthma,
eczema, allergic rhinitis and eosinophilia of >20
year’s duration
– wbc 10,000 - 40,000 with 30-40% eosinophils (4,000-
8,000/mm3)
– numerous extensive evaluations since 1982, including bone
marrow examinations, parasite serologies, rheumatologic
evaluation, CT scans, echocardiograms, PFTs,… reveal
only mild reversible obstructive pulmonary disease and mild
eczema

4. Case 2
28 year old man with no past medical history who
presented with signs and symptoms of severe
right-sided congestive heart failure in the setting
of marked eosinophilia
– wbc 14,400 with 63% eosinophils (9,072/mm3), aneia,
platelets 90k
– echocardiogram: dilated cardiomyopathy, fibrotic
material filling the right ventricle, moderate to severe
MR and TR, small pericardial effusion
– endomyocardial biopsy: focal fibrosis
– bone marrow: hypercellular with marked eosinophilia,
no blasts, mild fibrosis

5. Case 2 (continued)
A diagnosis of hypereosinophilic
syndrome was made and he was
treated with high dose steroids and
hydrea without response
Approximately 10 months after he
presented, imatinib mesylate therapy
was started with complete
hematologic remission
One month later he developed
hemoptysis, fever and chills and died
of presumed sepsis

6. Questions
What are eosinophils?
What do eosinophils do?
What are the causes of eosinophilia?
Why do some people develop problems
from eosinophilia and others not?

7. What are eosinophils?
Eosinophils are terminally differentiated cells of the
myeloid lineage that stain red with negatively
charged eosin
PMN
cytokines
IL3, GM-CSF, IL5
IL5
CD34+
HSC CMP GMP
No or low GATA-1
GATA-1, FOG,
GATA-1, PU.1,
PU.1, C/EBPα
C/EBPα
transcription
factors MΦ

8. Eosinophil life cycle
1-2% of peripheral
blood leukocytes; t1/2
in blood = 18 hours
>90% of eosinophils are
found in the tissues,
particularly those tissues
which interface with the
environment (BM, lymphoid
tissue, lower GI tract, and
uterus)
(from Rothenberg 1998 NEJM)

9. Normal eosinophil morphology
secondary granules bilobed
(core and matrix) nucleus
cationic proteins (EDN, MBP,
ECP, EPO)
enzymes (lysozyme, elastase,
cathepsin D,…) lipid bodies
cytokines (IL4, IL5, IL6,…) cyclooxygenase,
lipoxygenase,
primary leukotrienes,
granules EPO,…)
Charcot-
Leyden
protein

10. Questions
What are eosinophils?
What do eosinophils do?
What causes eosinophilia?
Why do some people develop problems
from eosinophilia and others not?

11. What we can learn from ?
there are no reported cases of a congenital
lack of eosinophils in humans, although
eosinophil-free mice have recently been
engineered (EPO-DTN mice, Lee et al. Science 2004; Δdbl
GATA Humbles et al. Science 2004)
eosinophil-free mice appear normal, but have
altered responses to allergen challenge
effect in helminth infection depends on model
schistosomiasis – no effect (Swartz et al. Blood 2006)
strongyloidiasis – impaired resistance to seocndary infection
(Knott et al. Int J Parasitol 2007)

12. What about humans?
– Host defense against helminth infection
– Anti-tumor effector cells
– Reproduction/mammary gland
development
– Wound repair and tissue remodeling
– MHC class I-restricted thymocyte
depletion
– Modulation of the immune response
Antigen presentation
Cytokine secretion
…..

13. Questions
What are eosinophils?
What do eosinophils do?
What causes eosinophilia?
Why do some people develop problems
from eosinophilia and others not?

14. Eosinophilia
Peripheral blood eosinophil count > 450/μl
Occurs in 5-10% of travelers
May be suppressed by:
– bacterial and viral infections
– fever
– corticosteroids
Diurnal variation

15. Eosinophilia: differential diagnosis
Allergy/Asthma
Drug hypersensitivity
Connective tissue disorders (Churg-Strauss
vasculitis, SLE, RA)
Parasitic infection
Neoplasm
Other (idiopathic hypereosinophilic syndrome, eosinophilic
gastroenteritis, Loeffler’s syndrome, hypoadrenalism, HIV...)

16. Eosinophilia and drug reactions
Eosinophilia may be provoked by a wide variety
of drugs
Drug reactions may be asymptomatic or
associated with characteristic signs and
symptoms
– Asymptomatic- quinine, PCNs, cephalosporins, quinolones
– Pulmonary infiltrates-NSAIDs, sulfas, nitrofurantoin
– Hepatitis - tetracyclines, semisynthetic PCNs
– EMS - L-tryptophan contaminant
– Interstitial nephritis- cephalosporins, semisyn. PCNs
– Drug rash with eosinophilia and systemic symptoms (DRESS) -
anti-epileptics, NSAIDs, antibiotics,…

17. Eosinophilia and nonparasitic
infectious diseases
Most acute bacterial and viral diseases
are associated with eosinopenia
Exceptions include:
– Bacteria: resolving scarlet fever, chronic
tuberculosis
– Fungi: coccidiomycosis, allergic
bronchopulmonary aspergillosis (APBA)
– Viruses: HIV

18. Eosinophilia and protozoan
infections
Not characteristic with the exception of
Isospora belli infection
(image courtesy of CDC DPDx)

19. Eosinophilia and ectoparasites
Scabies
– sensitization to the mites and
their eggs causes itching,
erythema, rash, and may cause
eosinophilia
Myiasis
– Infestation by fly larvae has rarely
been associated with
hypereosinophilic syndrome
(images courtesy of CDC DPDx)

20. Helminth causes of eosinophilia
Angiostrongyliasis Echinostomiasis Metagoniamiasis
Anisakiasis Enterobiasis Opisthorciasis
Ascariasis* Fascioliasis* Paragonomiasis*
Capillariasis Fasciolopsiasis* Schistosomiasis*
Clonorchiasis* Filariasis Sparganosis
Coenurosis Gnathostomiasis Strongyloidiasis*
Cysticercosis Heterophyiasis Trichinosis*
Dicrocoeliasis Hookworm* Trichuriasis
Echinococcosis Hymenolepsiasis VLM
marked hypereosinophilia (>3000/μl)
* early in infection

21. Eosinophilia of several years’
duration
Cysticercosis Flukes
Echinococcosis – schisto,
Filariasis fascioliasis,
– loiasis, clonochiasis,
onchocerciasis, paragonimiasis
mansonellosis, Hookworm
TPE
Strongyloidiasis
Gnathostomiasis
(image courtesy of CDC DPDx)

22. Unexplained eosinophilia
≥ 50% of cases of eosinophilia remain
unexplained despite exhaustive
diagnostic evaluation
Empiric anthelmintic therapy vs.
observation?

23. Hypereosinophilic syndromes
A group of heterogeneous disorders characterized
by:
– the presence of marked peripheral eosinophilia
>1500 eosinophils/mm3 on at least two occasions 6 months apart
– the lack of a secondary cause
ex. drug reaction, parasite infection, neoplasm
– evidence of end organ dysfunction
attributable to the eosinophilia or
otherwise unexplained in the clinical setting

24. End Organ Involvement in HES

25. Treatment of HES
Prednisone
Hydroxyurea
Interferon-α
Imatinib mesylate
(monoclonal anti-IL5 antibody)
Other agents for which there is data from case
reports and small series
–cyclosporin A, 2-CDA, vincristine,
chlorambucil, bone marrow transplant,
allogeneic stem cell transplant, alemtuzumab

26. HES subtypes
Myeloproliferative Undefined Associated
variant
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

27. Myeloproliferative variant HES/CEL
FIP1L1/PDGFRA-associated CEL
Etiology unknown
– FIP1L1/PDGFRA-negative
– Clonal eosinophils OR > 4 of the following:
dysplastic eosinophils on peripheral smear
serum B12 >1000 pg/ml
serum tryptase > 12
anemia and/or thrombocytopenia
hepatosplenomegaly
bone marrow cellularity > 80%
spindle-shaped mast cells
myelofibrosis
Chronic eosinophilic leukemia
– Demonstrable cytogenetic abnormalities and/or increased
blasts

28. FIP1L1/PDGFRA-associated CEL
Caused by an interstitial deletion in chromosome 4
that leads to a constitutively activated fusion tyrosine
kinase
Almost exclusively in men, 20-40 years of age
50% 5 year fatality rate prior to the discovery of the
tyrosine kinase inhibitor, imatinib mesylate

29. Tissue fibrosis is a common
sequela of F/P-HES
F/P-HES HES*
(n=14) (n=29)
Endomyocardial 6/14 3/29
fibrosis (43%) (10%)
Restrictive 5/14 2/29
pulmonary (35%) (7%)
disease
Myelofibrosis 6/11 rare
(54%)
* one patient presented with liver
abnormalities; eosinophilia and bridging
fibrosis was seen on biopsy biopsy

30. HES subtypes
Myeloproliferative Undefined Associated
HES
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

31. Lymphocytic variant HES
Associated with the presence of clonal
lymphocyte populations with aberrant
phenotypes (ex. CD3+CD4-CD8- and CD3-
CD4+) that produce eosinophilopoietic cytokines
Equally common in men and women
Predominance of skin manifestations
Often associated with elevated serum IgE, TARC
levels
May progress to lymphoma
No response to imatinib

32. HES subtypes
Myeloproliferative Undefined Associated
HES
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

33. Overlap HES
eosinophilic disorders in which tissue
infiltration is restricted to a single organ
peripheral eosinophilia >1,500/mm3 may be
present
– ex. eosinophilic gastrointestinal disorders, chronic
eosinophilic pneumonia, eosinophilic cystitis,
Churg-Strauss vasculitis
may be difficult to distinguish from undefined
HES

34. HES subtypes
Myeloproliferative Undefined Associated
HES
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

35. Associated HES
Recognized primary disorders associated with
peripheral eosinophilia >1,500/mm3 most
commonly as a result of immunodysregulation
Eosinophilia resolves with treatment of
underlying disorders
Complications of eosinophilia are rare
– ex. sarcoid, inflammatory bowel disease, ALPS

36. HES subtypes
Myeloproliferative Undefined Associated
HES
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

37. Familial eosinophilia
Autosomal dominant
Gene mapped to chromosome 5q31-33
Eosinophilia begins at birth, but only a small
subset develop end-organ damage
Lack of clinical manifestations is associated
with a relative lack of eosinophil activation
compared to other eosinophilic disorders

38. HES subtypes
Myeloproliferative Undefined Associated
HES
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

39. HES subtypes
Myeloproliferative Undefined Associated
HES
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

40. HES subtypes
Myeloproliferative Undefined Associated
HES
Lymphocytic
variant
Overlap Familial
* Klion A et al, Approaches to the treatment of hypereosinophilic syndromes:
a workshop summary report, J Allergy Clin Immunol 2006

41. Undefined
Benign
– prolonged asymptomatic eosinophilia >1500/mm3
Complex
– signs and
symptoms of
multiorgan
involvement
Episodic

42. Questions
What are eosinophils?
What do eosinophils do?
What causes eosinophilia?
Why do some people develop problems
from eosinophilia and others not?

43. Eosinophil activation
Altered phenotype
Density
-hypodense
Light microscopy
-dysplasia
-cytoplasmic clearing
EM Enhanced functions
-piecemeal degranulation Prolonged survival
-increased lipid bodies Adhesion
Surface marker expression ADCC
-increased CD69, CD44, CD25, Chemotaxis
HLADR Mediator release
-decreased CD23 -ECP, MBP, EDN, LTC4
Cytokine production
-IL8, GM-CSF, IL5,…

44. Activated eosinophils have altered
morphology
Piecemeal degranulation
Lipid body
Cytoplasmic clearing
Dysplastic nucleus

45. Serum levels of eosinophil granule proteins vary
depending on the etiology of the eosinophilia
8790
4245
>1500
EDN
1000
500
0
NL FE HES PARA
NL FE HES PARA
(n=16) (n=15) (n=7) (n=8)
GM eos/mm3 252 3314 5607 4639
(range) (95-520) (2184 - (1900-27492) (1508-10496)
5292)

46. Eosinophil surface molecules
CD23
Adapted from Rothenberg Ann Rev Immunol 2004

47. Eosinophil numbers do not correlate with expression of
surface activation markers
60 CD69 60
CD25 10
CD23
50 50 8
40
%CD69+ EOS
40
% CD25+ EOS
%CD23+ EOS
6
30 30
4
20 20
2
10 10
0 0
0 0 5 10 15 20 25 30 0 5 10 15 20 25 30
0 5 10 15 20 25 30
Eos/mm3 x 10^3 EOS/mm3 x10^3
EOSx10^3

48. Surface expression of the activation markers CD69 and CD25
on eosinophils is increased in patients with eosinophil-
mediated tissue damage
60
50
%CD69+ eos
40
30
20
10
0
MHES HES PARA
p < 0.01

49. Eosinophil-mediated pathogenesis
Direct cytotoxic effects
– Eosinophil granule proteins
– Reactive oxygen intermediates
Recruitment of other inflammatory cells
Fibrogenesis

50. Eosinophils and fibrosis
Eosinophils have been associated with
fibrotic conditions of various etiologies
– Hypereosinophilic syndromes, tropical endomyocardial
fibrosis, scleroderma, idiopathic pulmonary fibrosis,
asbestos-induced lung fibrosis, retroperitoneal fibrosis,
chronic asthma, eosinophilic esophagitis, chronic
schistosomiasis
Eosinophils possess a number of pre-formed
mediators that are thought to be pro-
fibrogenic
– These include TGF-β, IL-4, IL-6, TNF-α, ECP, and MBP

51. Eosinophils and fibrosis
Munitz and Levi-Schaffer
2004