Ige

190 kDa glycoprotein found in the gamma globulin fraction in serum immunoelectrophoresis. IgE accounts for only 0.004% of serum immunoglobulins and has the typical shape of the Y, similar to IgG or IgD, but a longer stem.

IgE production is detectable from the 11th week of gestation. IgE is detectable in the cord blood of approximately 50% of newborns. The plasma half-life of IgE is about 2 days.

The pathogenetic significance of allergen-specific IgE in rhinitis allergica and bronchial asthma consists in IgE-mediated activation of inflammatory cells, especially mast cells by allergens with consecutive liberation of preformed and newly generated mediators. IgE binds to mast cells or basophilic granulocytes via Fc receptors and can persist there for years. It also plays an important role in the defence against parasites and worms. An IgE-dependent cytotoxicity mediated by eosinophil granulocytes is assumed.

Indications for the determination of total IgE are mostly given in connection with the determination of specific IgE:

• In the presence of an atopic disposition.
• Total IgE in cord blood: A value can only be assessed if contamination with maternal blood is excluded. An increase in umbilical cord IgE >0.9U/ml can be considered a predictive parameter for atopic risk.
• As an interpretation aid for the assessment of the specific IgE.
• In parasitoses (especially in blood eosinophilia with negative parasite findings (tropical eosinophilia):
  • Filariasis
  • Trichinosis
  • Toxocariasis
  • Capillaria philippensis.
• After certain infectious diseases:
  • Mycoplasma infections
  • Pertussis
  • Measles
  • RSV bronchioliitis.
• In congenital or acquired immune deficiencies:
  • Wiskott-Aldrich syndrome
  • ataxia teleangiectatica
  • Nezelof Syndrome
  • Di George syndrome
  • Hyper-IgE Syndrome
  • HIV infection (especially in the late stage, with pronounced depletion of CD4 cells, development of an atopia-like syndrome with excessively elevated IgE)
  • T-cell lymphomas (especially in erythrodermic T-cell lymphomas, e.g. in the Sezary syndrome; see also lymphoma, cutaneous T-cell lymphoma).
• As a supplementary diagnosis for diseases which may be associated with atopy:
  • Urticaria
  • Angioedema
  • Gastroenteritis, eosinophilic
  • Exanthema of unexplained etiology
  • Drug exanthema (see below drug reaction, adverse drug reactions)
  • Alveolitis, allergic
  • Wegener's granulomatosis
  • Churg-Strauss syndrome.

Specific IgE (sIgE) is determined in serum, whereby only circulating sIgE is detected. Cellular sIgE, however, is not. The patient's serum is incubated on an allergen-containing matrix, after which the sIgE is quantified, for example using a fluorescent antibody (fluorescent enzyme immunoassay - (FEIA).

Other methods are:

• Enzyme Allergo Sorbent Test (EAST) in which specific IgE is detected with the help of enzyme conjugates.
• These non-radioactive methods have largely replaced radioactive methods such as the radio-allergo sorbent test (RAST). However, the term RAST is still often used in everyday life for the detection of specific IgE.
• The determination of drug-specific IgE is typically performed in cases of suspected IgE-mediated immediate type reactions. However, validated commercial tests are only available for a small number of drugs (mainly beta-lactams).

1. Buss YA et al (2007) Chronic urticaria--which clinical parameters are pathogenetically relevant? A retrospective investigation of 339 patients. J Dtsch Dermatol Ges 5: 22-27
2. Renz H et al (2009) In vitro allergy diagnostics. Guideline of the German Society for Allergology and Clinical Immunology (DGAKI) Allergo J 19: 110-128