Immunoglobulin G (IgG) is a multimeric immunoglobulin, built of two heavy chains γ and two light chains. Each complex has two antigen binding sites. This is the most abundant immunoglobulin and is approximately equally distributed in blood and in tissue liquids, constituting 75% of serum immunoglobulins in humans. In birds, IgG is often called IgY, and is found in serum and yolk.

Immunoglobulin G (IgG) is the only isotype that can pass through the human placenta, thereby providing protection to the fetus in its first weeks of life before its own immune system has developed. Immunoglobulin G (IgG) binds to many kinds of pathogens, for example viruses, bacteria, and fungi, and protects the body against them by complement activation (classic pathway), opsonization for phagocytosis and neutralization of their toxins. Immunoglobulin G (IgG) can cause food allergy, and in such causes delayed-onset food allergy, in contrast to food allergy by IgE, whose effects appear rapidly.

We can offer an ELISA method to detect the levels of Immunoglobulin G (IgG). In a first incubation step, the Immunoglobulin G in the samples is bound to polyclonal rabbit antibodies (in excess), which are immobilized to the surface of the microtitre wells. To remove all unbound substances, a washing step is carried out. In a second incubation step, a Peroxidase-labelled anti Immunoglobulin G (POD-antibody) antibody is added. After another washing step, to remove all unbound substances, the solid phase is incubated with the substrate, tetramethylbenzidine (TMB). An acidic stop solution is then added to stop the reaction. The color converts from blue to yellow. The intensity of the yellow color is directly proportional to the concentration of Immunoglobulin G in the sample. A dose response curve of the absorbance unit (optical density, OD) vs. concentration is generated, using results obtained from the calibrators. Immunoglobulin G, present in the patient samples, is determined directly from this curve.