The canonical antibody structure (typically IgG) is composed of four polypeptide chains:
: Forms the base and lower parts of the arms. It determines the antibody's class and how it interacts with other parts of the immune system. Fab and Fc Fragments :
: It consists of two identical heavy chains (~50 kDa each) and two identical light chains (~25 kDa each), held together by disulfide bonds.
