Indicator Explainer
IgG4
Along with the immunoglobulin G3 subclass (IgG3), the IgG4 subtype makes up a minor part of circulating antibodies in healthy individuals. The IgG4 core hinge sequence contains 12 amino acids and two interchain disulfide bonds.This subtype has moderate affinity for binding Fc receptors and does not bind complement component C1q. The production of IgG4 can be stimulated following repeated or long-term exposure to antigen. Elevated levels are found in various diseases and infections and can be indicative of an fibroinflammatory syndrome known as IgG4-related disease.
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Source: National Cancer Institute, NCI Thesaurus 26.09d, C78227. NCI definition, reproduced without modification under CC BY 4.0. Source identity and definition checked automatically on 2026-10-20. No individual clinical interpretation or human reviewer is asserted.
Reading results
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.
Also Known As
References
- NCI Thesaurus 26.09d — IgG4 (C78227)
- Source: National Cancer Institute, NCI Thesaurus 26.09d, C78227. NCI definition, reproduced without modification under CC BY 4.0.
- Isotype-specific autoantibody profiles associated with clinical immunological signatures in IgG4-RD. — Rheumatology (Oxford), 2026-10-19 (PMID 42898012; literature)
- IgG4-Related Disease Presenting as Inflammatory Midline Pseudotumor of the Face and Neck. — Int J Dermatol, 2026-10-16 (PMID 42885337; literature)
- Lumps, Bumps, and Diagnostic Stumps: A Case Report of IgG4-Related Disease. — Clin Case Rep, 2026-10-23 (PMID 42920875; literature)
- Economic burden and quality of life of IgG4-related disease in China: A comparative analysis of three treatment regimens. — Rheumatol Immunol Res, 2026-10-22 (PMID 42924285; literature)
- Persistent fibrosis in IgG4-related disease: Stromal mechanisms, biomarkers, and therapeutic implications. — Chin Med J (Engl), 2026-10-26 (PMID 42934087; literature)
- Effectiveness of tocilizumab monotherapy for IgG4-related disease-like features caused by idiopathic multicentric Castleman's disease: a case-based review. — Rheumatol Int, 2026-10-22 (PMID 42911255; literature)