Immunoglobulin G (IgG) is a type of antibody found in blood and other bodily fluids. It plays a crucial role in the immune system by identifying and neutralizing pathogens like bacteria and viruses. IgG is the most abundant antibody, making up about 75-80% of the total immunoglobulin in the body. IgG is unique because it can cross the placenta, providing passive immunity to the fetus during pregnancy. It also has a long half-life, allowing it to remain in the bloodstream for an extended period. This characteristic makes IgG important for long-term protection against infections.