This document discusses the main types of antibodies (immunoglobulins) in the human body: IgG, IgM, IgA, IgD, and IgE. IgG is the most common antibody type found in blood and tissues. IgM is the first antibody produced during an initial immune response. IgA functions in external secretions, while IgD plays a role in immune system development. IgE helps fight parasites but can also trigger allergic reactions when overactive.