An antibody (Ab), sometimes known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. This infographic presents the following aspects of types and formats of antibodies: 

• The definition of antibody isotypes, allotypes, and idiotypes 
• Isotypes of human antibodies and their functional properties 
• Special and engineered formats of antibodies