Yes, there are four different IgG antibodies. IgG refers to a class of antibodies that is composed of four different subtypes of IgG molecules. The four IgG subclasses are designated as IgG1, IgG2, IgG3 and IgG4, listed in decreasing order of abundance in the serum.

All four IgG subclasses contain antibodies against components of a wide range of disease-causing viruses and bacteria. Although the different IgG subclasses have similar amino acid structures, each subclass varies from the others with respect to their functions in protecting the body against infection. 

• IgG1 antibodies are generated when an organism experiences an allergic or anaphylactic reaction to a substance.
• IgG2 antibodies are associated with the host reaction to bacterial capsular polysaccharide antigens. Deficiency of IgG2 increases vulnerability to certain bacterial infections.
• IgG3 antibodies are produced in response to foreign antigens or when the human body becomes infected with a parasite. 
• IgG4 antibodies act as biological markers for several autoimmune diseases such as asthma, pancreatitis, and certain allergies. Significantly higher levels of IgG4 are indicative of an immune response.

The percentage of each IgG subclass present in the bloodstream changes with age.