An immunoglobulin fragment composed of one variable domain from an IMMUNOGLOBULIN HEAVY CHAIN or IMMUNOGLOBULIN LIGHT CHAIN
An immunoglobulin fragment composed of one variable domain from an IMMUNOGLOBULIN HEAVY CHAIN from the serum of camelids (ALPACAS, LLAMAS, CAMELS, and DROMEDARY)
A variable domain fragment from the ancestral IMMUNOGLOBULIN (termed 'novel antigen receptor' or IG-NAR) of cartilaginous fish such as SHARKS