Immunoglobulin g4

IgG4 immunoglobulins represent a subclass of the immunoglobulins G.

The immunoglobulin G (IgG) can be divided into 4 subclasses:

• IgG1, the largest IgG subclass mediates like IgG3 the immune response to protein and polypeptide antigens
• IgG2 mediates the immune response to polysaccharide antigens
• IgG4 can block an IgE response and is found elevated in various allergic immune responses. However, the role of allergen-specific IgG/IgG4 in the pathogenesis of allergic immediate type reactions is unknown. On the other hand, IgG4 plays an essential role in IgG4-associated autoimmune diseases.

The IgG4 antibodies of class G represent the smallest proportion of the IgG subclasses in the blood of healthy people. IgG4 antibodies are mainly formed in allergic reactions, especially in food allergy. IgG4 can block an IgE response and is found elevated in various allergic diseases. It increases to different degrees with different immunotherapies (hyposensitizations). It increases to different degrees during various immunotherapies (hyposensitizations) and enables statements to be made about the biological value of the measure carried out.

The so-called IgG4-associated diseases are rare, autoimmunological (allergic?) multi-organ diseases affecting pancreas, kidney, lung, lymph nodes, thyroid, liver, eyes, naso-pharynx and skin. Clinically, pseudotumorous swelling may impose.

IgG4 increased:

• Infections, multiple myeloma, lymphomas, malignancies, autoimmune diseases (see also immunoglobulins). High IgG4 concentration is an indication of an IgG4-associated autoimmune disease (e.g. IgG4-associated pancreatitis) in appropriate clinical settings.

IgG4 decreased:

• Primary immunodeficiencies; association with: atopic diseases, autoimmune diseases (SLE, Sjögren's syndrome, vasculitis), chronic active hepatitis, diabetes mellitus, nephrotic syndrome

Expensive and useless is the determination of IgG4 in food allergies. Such "screening tests" are used by various companies. Institutions offer such "screening tests". The high costs involved are justifiably not reimbursed by German health insurance companies (see the corresponding position papers of the professional associations).

1. Bookhout CE et al (2016) Immunoglobulin G4-Related Lymphadenopathy. Surg Pathol Clin 9:117-129.
2. Freiberger SN et al. (2016) IgG4 but no IgG1 antibody production after intralymphatic immunotherapy with recombinant MAT-field1 in human. Allergy doi: 10.1111/all.12946.
3. Kollmann D et al (2016) The quantity and quality of α-gal-specific antibodies differ in individuals with and without delayed red meat allergy. Allergy doi: 10.1111/all.12948.
4. Renz H et al (2002) In vitro allergy diagnostics. Position paper of the German Society for Allergology and Clinical Immunology (DGAKI). Working group "In Vitro Allergy Diagnostics" of the Section of Immunology. Allergo J 11: 492-506
5. Stack SO et al (2008) EAACI Task Force. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy 63: 793-796
6. Zeng G et al (2016) Longitudinal profiles of serum specific IgE and IgG4 to Dermatophagoides pteronyssinus allergen and its major components during allergen immunotherapy in a cohort of southern Chinese children. Mol immunol 74:1-9.

Age-adapted standard values for IGG4:

Age group (years) Value (mg/dl)

• 0 - 1 < 0.8 mg/dl
• 1 - 2 < 40.8 mg/dl
• 2 - 3 0.6 - 68.9 mg/dl
• 3 - 4 1.2 - 93.8 mg/dl
• 4 - 6 1.7 - 115.7 mg/dl
• 6 - 9 3.0 - 157.7 mg/dl
• 9 - 12 4.3 - 190.0 mg/dl
• 12 - 18 5.2 - 196.1 mg/dl
• 18 - 120 5.2 - 125.0 mg/dl