From the Guidelines
The presence of IgG in a respiratory allergy profile is not beneficial in identifying specific allergen triggers and does not necessarily indicate an active allergy. According to the clinical practice guideline on allergic rhinitis 1, IgG testing is not recommended for diagnosing respiratory allergies as it does not provide useful information for guiding targeted therapy. The guideline states that allergy testing can be considered in patients who do not respond to empiric treatment, but it emphasizes the use of specific IgE testing, either skin or blood, to confirm the diagnosis of allergic rhinitis.
Some key points to consider when interpreting IgG results in a respiratory allergy profile include:
- IgG antibodies typically represent a normal immune response to substances encountered before, and their presence does not necessarily mean an active allergy 1
- Respiratory allergy symptoms are primarily mediated by IgE, not IgG, making IgE testing more appropriate for identifying true allergies 1
- The measurement of total IgE also has limited diagnostic value in the diagnosis of allergic rhinitis, and testing for non-IgE antibodies, such as IgG, is not beneficial 1
In clinical practice, if you're experiencing respiratory symptoms, IgE testing is more appropriate for identifying true allergies, and consultation with an allergist is recommended to perform appropriate diagnostic tests, including skin prick tests or specific IgE blood tests 1.
From the Research
Presence of IgG in Respiratory Allergy Profile
The presence of IgG in a respiratory allergy profile is associated with allergen-specific tolerance, either naturally induced or generated by specific immunotherapy 2. Allergen-specific IgG antibodies play a significant role in allergen-specific tolerance, but the underlying mechanisms are still debated.
Role of IgG in Allergic Disease
IgG antibodies usually recognize different epitopes on allergens compared with IgE and do not efficiently interfere with allergen-induced inflammation 3. However, IgG antibodies to important IgE epitopes can be induced by allergen-specific immunotherapy or by passive immunization, leading to competition with IgE for binding with the allergen and preventing allergic responses.
Key Points
- Allergen-specific IgG antibodies are associated with allergen-specific tolerance 2
- IgG antibodies do not efficiently interfere with allergen-induced inflammation 3
- IgG antibodies can be induced by allergen-specific immunotherapy or by passive immunization to prevent allergic responses 3
- The presence of IgG in a respiratory allergy profile is not recommended as a diagnostic tool in IgE-mediated allergy 2
Relationship between IgE and IgG
The risk of respiratory symptoms on allergen exposure increases with increasing specific IgE levels 4. While IgE is the primary antibody responsible for allergic reactions, IgG antibodies can modulate the allergic response by competing with IgE for binding to allergens 3.
Immunotherapy and IgG
Allergen-specific immunotherapy can induce large increases in anti-allergen IgG4 antibodies, which can help reduce the allergic response 5. This therapy can be administered either subcutaneously or sublingually, and has been shown to be effective in reducing symptoms of allergic rhinitis and asthma 5.