Immunoglobulin E (IgE)

Sample

• The best sample is fresh serum.

Indication

1. Used to detect allergic diseases.
2. Advised when the patient have:
   1. Itching of the skin, and itching of the eyes.
   2. Urticaria and hives.
   3. Asthma and difficulty in breathing.
   4. Skin diseases like eczema.
   5. A cough, congestion.
   6. Sneezing.
   7. Persistent diarrhea, nausea, and vomiting.

Pathophysiology

1. IgE exists as a monomer form with a molecular weight of 190,000 and is 7S.
2. It has an extra domain in the constant portion.
3. It has:
   1. Two epsilon (ε) heavy chains.
   2. One pair of kappa (κ) or lambda (λ) chains.
4. It’s Fc region binds strongly to the receptors on the mast cells and basophil along with antigens.
   

   IgE Molecular Structure

3. It is 0.004 % of the total immunoglobulins.
4. Its half-life is 2 days.
5. It is mainly involved in type 1 hypersensitivity reaction.
6. It cannot activate the complement system via the classical pathway.
7. It is present in the serum of a healthy person is extremely low concentration.
8. It attaches to the receptors on basophils and mast cells.
   

   Type 1 hypersensitivity Reaction and role of IgE

8. There are low-affinity receptors present on the surface of B-lymphocytes and eosinophils.
9. It can not cross the placental barrier.

Normal Value

Source 1

Age	IU/mL
Cord blood	At term ∼1% of the maternal value
0 to 4 days	<1.5
5 days to 12 month	<15
1 to 5 year	<60
6 to 9 year	<90
10 to 16 year	<200
>16 year	<100
Adult	3 to 423

• To convert into SI unit x 1.0 = kIU/L

Another source

• 150 ng/ml on the topic (non-allergic) person.
• or  .002 to 0.2 mg/dl
  • Values vary because of the methodology used.

The raised level is seen in:

1. Allergic diseases like asthma, skin diseases.
2. Parasitic infestation
3. Multiple myeloma producing monoclonal IgE.
4. Hyper IgE syndrome.

The decreased level is seen in:

1. Agammaglobulinemia.

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