Indicator Explainer
IgG1
The most abundant immunoglobulin G (IgG) subclass in the circulation of healthy individuals. The IgG1 core hinge sequence contains 15 amino acids and two interchain disulfide bonds. This subtype has high affinity for binding both Fc receptors and complement component C1q. IgG1 is the predominant antibody subclass that responds to antigens derived from both soluble and membrane proteins. Reduced levels of circulating IgG1 can indicate the presence of a variety of primary and secondary antibody deficiencies, which can result in hypogammaglobulinemia.
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, C201279. 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.