blood immunoglobulin G level blood immunoglobulin G1 level 2026-09-08T09:20:23Z CMO:0004167 Measurement of the amount in blood of the G1 subclass of immunoglobulin G (IgG), the most abundant class of antibodies found in blood serum and lymph. IgG antibodies are active against bacteria, fungi, viruses, and foreign particles, and trigger action of the complement system. IgG subclasses differ in the structure of their hinge regions. IgG1 is the most abundant subclass in serum, and is able to activate complement and bind to the Fc receptor on phagocytic cells. blood IgG1 level caripark clinical_measurement_ontology