Hypersensitivity

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This section deals with clinical conditions associated with hypersensitivity which are covered by the Immunology department. For each clinical condition, the relevant immunological tests are listed together with a short explanation of their use.

Bronchopulmonary aspergillosis, Aspergilloma and Hypersensitivity pneumonitis

Relevant immunological tests: Aspergillus precipitins

In bronchopulmonary aspergillosis and aspergilloma a mixture of IgE and IgG antibodies are usually present. Bronchopulmonary aspergillosis can be caused by species other than A. fumigatus.

In allergic rhinitis and asthma, where aspergillus is the relevant allergen, IgE antibodies dominate.

In hypersensitivity pneumonitis, IgG antibodies are usually present alone. IgG antibodies, without IgE antibodies can also be seen in some cases of sub acute invasive aspergillosis.

IgG antibodies are infrequent in healthy individuals.

Aspergillus antibodies are not a recommended test for the investigation of the majority of cases of invasive aspergillosis in immunocompromised hosts.

Farmer’s lung

Relevant immunological test: Farmer’s lung precipitins (thermophilic actinomyces)

Hypersensitivity to Micropolysporium faeni is a common cause of farmer’s lung hypersensitivity pneumonitis occurring 12 to 24 hours after exposure to mouldy hay. In some cases of farmer’s lung, hypersensitivity to other fungal species implicated.

The absence of precipitin (IgG) to Micropolysporium faeni does not rule the diagnosis out. These antibodies can be found in some healthy individuals: The presence of these antibodies supports, but does not confirm, a diagnosis of farmer’s lung.

There are numerous other causes of hypersensitivity pneumonitis including fungal spores and occupational antigens. Please discuss with the laboratory if these may be incriminated.

The diagnosis is made by a combination of clinical features, X-ray and lung function tests.

Bird fancier’s disease

Relevant immunological tests: Avian precipitins

The symptoms are similar to farmer’s lung but more commonly are of the chronic type. Precipitins (IgG) to avian proteins provide good evidence of the cause of the symptoms.

Coeliac disease

Patient information is available from the Coeliac Society.

Relevant immunological tests:

IgA antibodies to tissue transglutaminase are found in active coeliac disease, and can be used to monitor compliance with treatment. Similar antibodies are seen in dermatitis herpetiformis.

We may have to measure IgA to ensure that IgA deficiency (particularly common in these patients) is not causing a false negative result. IgG antibodies to tissue transglutaminase are utilized in IgA deficient patients.

(Last updated October 8th 2014)