There are four types of IgG - IgG1, IgG2, IgG3, and IgG4. These four IgG’s together make up 10% to 20% of human plasma. All four are an integral part of the body’s immune system. However, each of them have inherently different properties and functions. Each subclass has its own unique half-life, immune complex formation, complement activation, and antigen binding protocols. In addition, each subclass triggers their respective effector cells in different ways.

• IgG1 and IgG3 subclasses contain antibodies against toxins produced by the tetanus and diphtheria bacteria. They also contain antibodies against foreign antigens.
• IgG2 subclass is rich in antibodies against the polysaccharide covering of certain disease-causing bacteria such as Haemophilus influenzae and Streptococcus pneumoniae.
• IgG4 subclass is associated with multiple autoimmune diseases including pancreatitis, asthma, and certain allergies.